Not particularly into it myself, but yes, I would agree with you that dirty talk such as "Oh Yes! Fuck me harder!" or whatever, is totally different from role play where the SP and the punter are pretending to be certain characters. I'm not more well endowed than average, but I must admit that the occasional girl who has whispered "Wow, lovely big cock!" has turned me on quite a bit, even though I know they are exaggerating. Dirty talk doesn't seem to be very common though, in my experience.