The belief in part is that boys are far less likely to feel coerced by femals instructors. It’s very unlikely that a female teacher could physically overpower a male student.
The problem I have is that if it were a male teacher with a willing female student, he’s still be castigated and branded a sex offender, probably jailed for statutory rape, all kinds of stuff. Nobody is judging him on how good looking he is and how lucky the girl was for it.
With a female teacher and male student, it’s wink, wink, nudge, nudge, lucky boy if she’s hot and her guilt isn’t dependent on her actions but her looks.