I have a slightly different take on said vid.
Rabib seems fairly ho-hum about it all. I got the impression he is no stranger to bottoming. I didn't see him showing signs of pain neither at the initial penetration nor later when he was getting pounded.
What bothered me was that Rabib seemed to want to take a nap during the whole thing.
Except when he was riding Daxter. There he seemed in his element.
When David proposed that he bottom, I didn't see Rabib incenced by it all, I saw him acting chill and making a play for as much money as he could get out of it.
True, Rabib never did get hard, but some dedicated gay bottoms never do either.
Naturally I know none of this for a fact. It's just the impression I got from watching the vid.