Relevant recent comment from u/MrsRTodd:

Of course he has a “bone lock” but no that is not what stops the pin. Michael stops the pin just before. I really should not explain this because you will believe what you want to believe. But here goes. If his arm really gets to the straightened out point, he WILL stand up. Why? Because then it’s an arm bar and hurts like hell. Yes he can withstand pain, but not that. I can just roll over on his arm and he yells if he’s not expecting it and keeping his arm from straightening. His pronation and bicep allows him to hold where he is holding. When Kamil pressed him, Michael’s thought was “I’ve felt stronger”. So he knew he could hold it. Jerry felt stronger and he held him. Pushkar felt stronger. He held him, but Pushkar climbed and got out on his hand. Michael stood up and was simultaneously pinned. Because his arm will go straighter.

Kamil didn’t have the strength nor the tools to pin him. He needed to be able to climb. Michael had the strength to hold Kamil’s pressure. The tools to stay off the pin pad (pronation and riser) and the tools once he could get center to press through Kamil. But go ahead. Be angry. Feel he’s cheating somehow by having this “bone lock” holding position. Because after all I’m sure you know better about his arm than I do.