Ok you explained that that was the kid version but didn't explain the not kid version.

Zygote is XY or XX (at conception, which is generally understood as male, female) ??? Male baby, female baby

It's the ??? Or before part that I'm struggling to understand. Is it the low percentage of deviations that make it not definite at conception?

Fwiw I want you to be right. I see that gonadal sex is effectively female until male, but again the male part was predefined at conception.