I watched the fights this morning and I didn't think that Pallhares had any malicious intent to injury Pierce.
He held it MAYBE 2 seconds after Pierce tapped? True it might be long enough to do some damage, but that guys adrenaline is pumping like crazy.
We see guys get tagged in the liver and drop like flies, it doesn't mean they're out. Sometimes guys shout out in pain so I have the feeling he just wanted to be sure buddy tapped and everyone saw it.