The MF difference re casual sex has a simple explanation. It takes more effort for a male to find willing partners than it does for a female. It is the energy devoted to the search which detracts from academic performance, and that also explains why having a regular partner (with or without sex) may actually provide an academic advantage.
Now why do you say that?
It is quite possible to disprove one claim in a text without knowing everything else in the book.
You could say that "Calling bulls**t on a textbook requires you to know *better* about at least one item." But knowing *more* has nothing to do with it.