Good point. It’s hard to differentiate these things. Aptitude is important to measure here because that is generally the goal when it comes to learning skills for careers or life, and they’ll try to measure these learned abilities with aptitude tests. Ie: you might have taken the ‘Scholastic Aptitude Test’ (SAT) in high school. One of the possible considered reasons for this discrepancy is just that males are better at taking tests and/or females are better at classwork, discussed in the first linked study.

From what I understand because I haven’t read more than the abstracts and intros is that the second study was supposed to have accounted for that idea and still found statistical bias.