My second and third paragraph should have that covered.
If it is a situation where you know you get horny and someone is trying MDMA for the first time, you don't disclose that you do get horny, and you have sex. I would say that is a gray area that leans towards bad.
My first time trying edibles was with someone that I already had sex with and was planning on having sex with that night. If we got horny from that and fucked sooner than expected then that would be fine.
I guess to sum up, if you put someone in a situation where they don't have knowledge of the possibilities that is bad. Everyone already feels this when it comes to other things. Like hidden fees. They said x but y happened. Why should I expect y to happen? This is a new situation and I'm ignorant and you took advantage of it. Even if I got what I originally wanted the "price" changed.