@MaleNagisa I think the reason Great was sent there is somehow Fake Y's plan and Jin allowed it thinking it was what was needed.
But Burner is the odder one since, because she wasnt the perfect one, she should have just been raised alongside the other siblings with 80% - 99%. There wasnt a need for her to have some special treatment if she wasnt perfect and especially after Great was born.
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It also could be that because she was female that she didnt reach 100%. Not a sexist thing exactly, had Bear been female then Burner would probably be the perfect clone and Great would be the 2% off.
Or...Bear/Oren already knew the perfect child was male which is why they said that. Burner being female might not really mean anything, just she really didnt have 100% and Great did.
It didnt seem like Jin and Fake Y were specifically looking for a male, all the wording for the child was gender neutral.