I agree that it seemed to be held for a long time and very hard but it shows what can happen in extreme circumstances.
In the absence of any other such evidence, the damage will still happen to a lesser degree... it does show us that we need to take more care, even if we thought we were doing everything we could.
I've known all sorts of anglers squeeze their fish to make their fins go up for a photo.. carp, perch, zander, bass. Sad really that people even think it's okay. The way that some people hold perch with a horizontal lip hold and unsupported body is downright cruel imho.
Found this a while back and although it relates to US bass, perch have a similar mouth structure.