He might also find it difficult to fuck in front of a cameraman and maybe more. Or he could have jacked off beforehand in the fear he might blow too early.
Before the days of viagra you used to have to actually like pussy to be a pornstar. It didn’t matter if you had a big cock if you couldn’t get it hard. That’s why you always saw all the same guys in rotation because they were the only ones that could get it up reliably