His source is garbage, but he isn't wrong. Sexual phenotype is determined by exposure to hormones primarily during pregnancy, not karyotype.

Male phenotype XX karyotype and the reverse XY karyotype female phenotype are not that rare at all. Entirely possible it applies to you (yes, you, the person reading this), which is why they no longer have biochem students etc test their own karyotype as a lab practical in a lot of universities because its not the sort of thing you want to find out from doing a 2 credit lab.

This isnt even getting into XXY, XYY, etc. Which again are nowhere near as rare as you'd think due to sampling bias in the people who get karyotyped in the first place.

It's not ARCHEOLOGYwars either ;)

This is CODEwars, not BIOLOGYwars nor SOCIALSCIENCEwar. Please use Reddit for discussing your vision of XY chromosomes.

1. This is not a kata suggestion (Kata suggestions are ways to improve the kata)
2. The specific details are irrelevant to the task. Consider it a hypothetical task if you wish.
3. The source you linked is self-proclaimed to be "Social science", and not biology or chemistry. I would not base your understanding of biological sex on a comparitive study done in the field of social science, if I were you.

Sex of the fetus isn't determined at conception, rather it happens after 40+ days .

check out

Human Embryo’s Sex determination: A Comparative Study of Quran, Hadith and Science
http://web.uob.edu.pk/uob/Journals/Balochistan-Review/data/BR%2002%202015/169-176%20Human%20Embryo%E2%80%99s%20Sex%20determination%20A%20Comparative%20Study%20of%20Quran,%20Hadith%20and%20Science,%20Nosheen%20Zaheer.pdf