Sure, sexual fluids do not come from the backbone and neither do women produce a fluid directly involved in reproduction. The tafsir is wrong. How is the Quran affected?
As to the verse of sura kahf
Until, when he reached the setting of the sun, he found it set in a spring of murky water
is not the same as
Until, when he reached the setting of the sun, it was setting in a spring of murky water
which is the poor reading/understanding.
In 37:5,70:40 the Quran speaks of the mashaariq/places of sunrise (plural), and maghaarib/places of sunset (plural). The statements clearly point to the ephemerity of these places, certainly not fixed, so there isnt one single place of sunrise or sunset but each of those ephemeral sunrises and sunset spots where one can see the sun rising or setting when looking at the horizon must be referred to with a definite article when spoken of on their own, as in sura kahf above 18:86,90.
Mashaariq literally means "the places where the sun rises". The east can be implicit depending on one's position on Earth however "the places where the sun rises" can also include the south or the north as happens in certain Arctic/Antarctic times of the year. Thats how accurate and consistent the Quran truly is contrary to other similarily ancient religious scriptures, such as the Hebrew Bible from where it is claimed the Quran finds inspiration and which represents the faulty cosmic understanding of the people that penned it, speaking of
Isa45:6,Ps113:3"the rising of the sun to the place where it sets"
traveling across the heaven from one end to another Ps19:7, circling the earth Ecc1:5, as well as of a salvific figure coming
Isa41:25"from the rising of the sun"
or of the miraculous prolongation of daylight for 24 additional hours being due to the sun made to stand still, instead of the earth Josh10:12-14, or of how, towards the end of the day
"the sun descended very much"
until it set
"near Gibeah" Judges19:11-14
probably setting in the "dwelling" God has created for it somewhere in the heavens Ps19:5, the place where both the sun and moon stand still in the face of God's might Hab3:11. There is also mention of times where
1Sam11:9"the sun is hot"
which implies that there are others where it cools down which obviously is an assertion that ignores the fact that while the sun is "cool" in nighttime, the opposite side of the round Earth is still receiving the Sun's warmth. The Sun was moving backwards in relation to the Earth during the miraculous extending of daytime Isa38:8.
18:86,90 relate some of the prophet Dhul Qarnayn journeys across the Earth. The Quran describes, as a third party observer
, what he and the people he met experienced and saw in these places. 18:90 describes his arrival at the place of the rising sun, where he
saw it rising. Allah is describing the scene after the event had happened, Dhul Qarnayn travelled the land and at one point during his expedition saw the sun rising from where he was standing, and this is how he knew he had reached the rising place of the sun.
In that place out of many that was worth mentionning because of a particular people he met there, the Quran says the sun was rising "on a people" specificaly. The reason for singling out a group from among those standing there and saying the sun was on them was to convey a specific image, that these were "a people to whom We had given no shelter from It" meaning the blazing sun was affecting them only as an uncivilized and primitive people who did not cover themselves or build protection against the blazing sun, contrary to Dhul Qarnayn and his men who knew how to protect themselves from it. This is why the sun rising was worth mentioning in relation to them because it affected them particularly; they suffered from it. If by Dhul Qarnayn's reaching the rising of the sun, what is meant is that he reached a place with a hole in the ground out of which the sun comes out there will need to be an explicit statement from the Quran to come to that conclusion, a statement such as it saying it rose "from below" or "behind" or "in front of a people" instead of "on a people" otherwise nothing excludes this place being a spot from where the sun can be seen rising if one looks at the horizon. Obviously, there arent so many of those places around us and one must go to special and particular places to see it rising and setting at the horizon. Reaching the place of the rising sun does not mean the sun could be seen rising physically a few meters away, that place extends from the spot where one is standing to the physical position of the sun in outter space.
Similarly in 18:86, no civilisation ever believed, including the pre-Islamic Arabs, that the sun would sink in the water at night. People instead thought the sun rose and set at the flat Earth's edges which is why it should have said he found it setting behind the water, not in it had it meant Dhul Qarnayn reached a spot of physical sunset.
The message of this verse is that he reached a spot where he stopped his progress because of a water source/aynin which could refer to an ocean just as it could be a sea, or a vaste lake etc and that at this spot where he met a people, he saw the sun setting in the water which is what anyone sees when looking at the horizon of a vaste water expanse.
The verses are not interested in speaking of the places where the sun physically rises or sets, but in describing what the prophet king Dhul Qarnayn saw on his expeditions, more specifically the people he met which is why it speaks of several of his journeys including one inside a valley where his sight was blocked by the mountains and couldnt therefore see the sun rising nor setting 18:93.
A legitimate question one might ask is why mention these places of sunrise and sunset considering Dhul Qarnayn probably saw many sunsets and sunrises on his journeys. The answer is that after seeing many of those during his expeditions, he reached one of the countless places where the sun sets and rises if one looks at the horizon and these specific places were worth mentionning, contrary to all the spots where he could see the sunrise and sunset when looking at the horizon, because he met in them particular people whose characteristics are given in the verses 18:86-90 (disbelievers deserving punishement at the setting of the sun, very primitive people at the rising of the sun).