The first part of your argument applies to 51% of the population. For the remaining 49%, willfully performing the act (I do not count rape victims) definitely does indicate homosexuality. The second part of your argument is inarguable.
If someone put a gun to your child’s head and said “Do it or I kill the kid” and you do it, it doesn’t mean you are suddenly gay.
In order to “pitch”, you have to be aroused enough to get an erection. If you seek that, you are gay. A gay friend of mine used to “catch” for a large number of Muslim men who wanted to “pitch”. That tells me they were gay.