That was an Ura Sankaku Jime/Rear Triangle Choke while holding the leg for leverage and immobilization of the opponent, although I'm sure the pressure on the leg was tremendous. That technique is very rarely seen in a match, whoever is performing it is obviously very adept at Ne Waza. Sometimes legal moves are assisted by grabbing the leg of ones opponent to disrupt their base and mobility, I've also seen chokes where the leg was being stretched at a very awkward and seemingly painful angle.

had the same doubt myself, would be cool if someone enlightened us...

It wasnt really a kneebar. he was choking him with his legs. There was no significant leverage on the knee to qualify as a leglock hope my english is not too bad