I doubt you have spent time teaching undergraduate physics.Why do you doubt that? I did a bit of teaching during my PhD, though never an entire lecture course.
Your assertion that the male students might have dropped out because of the "frou-frou" exercise is easily construed as chauvinistic
This concerns me less than whether or not it's likely to be true.
Unless you are a female student in physical sciences or math, I don't think you can really understand what its like to be told, implicitly and explicitly, for most of your secondary and college education, that you are inferior to your male peers.
Ah, the old "unless you belong to group X you're not allowed to comment on this" line. I have nothing for this.
* But here's a hypothetical for you. You come to my company for a job interview.
When you come see me, I ask you what your favorite subject is and I let you talk about it for twenty minutes. Then we start talking about the job.
When you see Bob next door, he immediately starts drilling on topic.
Which interview do you perform better on?*
I have no idea. It's possible that the stress of being judged on what my favourite topic is might cause me to stress out even more. In any case, it's a pretty nonequivalent situation.
There are two types of physics students... the ones who are really at university to learn something else, and the ones who are at university to learn physics. I was in the latter category. Going to my first physics class and having it being a hand-holding exercise instead of a "listen up you pricks, F = ma and you'd better not forget" lecture would have seemed like a waste of precious lecture time. Of course, a female student could easily have felt exactly the same way.