Lakey, there is something a bit odd about that..
How could you retain a grip in some crack (no comments, please) doing those acrobatics? And why?
Interviews with dedicated freeclimbers contain a certain reality about their fate.
I wondered why he did it, but it seems to be to provide a higher platform for him to sit on so he can reach the higher handhold which he missed when trying to jump up.
How he jams his hand in I don't know.
He'll have callouses like you would not believe on his fingers and be perfectly able to take his full weight on a finger jam - basically he'll have rammed his fingers as far in to that crack in the wall as they would go and as long as his weight is on them they won't come out
If you or I tried it we'd rip the skin off and probably break bones too but experienced free climbers have built up the callouses and muscles from years of practice until they can use their fingers like a technical climber would use an aid