I re-watched the fight between Palhares and Pierce. Personally I don't believe he purposely held the hold longer than was needed and here is why. When he locked the hold on yes, there was no way he could not have felt pierce tap. However you are taught that you do not let go of the submission until the ref pulls you off. I think that the ref is mostly to blame for the situation. When he goes to break up the submission Palhares is looking back and up like he is supposed to and I am unsure if he seen the ref circle around. Anyway as the ref goes to break up the hold he shoves his head into Palhares stomach and starts pushing or pulling at his leg while pushing into his chest. Now personally when I am doing Juijitsu if someone is pushing on me when I have a heel hook locked on I assume it is my opponent. I can see a potential situation where Palhares did not realize that it was the ref trying to step in. It is just a thought, though on the other hand I know Palhares has a habit of doing this kind of thing. I like Palhares so I might just be grasping at straws.