Yep mine do that ESP when i give them shrimp i usually just gestimate how big to cut the shrimp and usually its to big not to worrie they will shake and tear it till it fits in there mouths
Yeah I have bichirs in my tank that do it all the time. If it's something that's too big for them to eat they deathroll pieces of it off and eat it. Also they do it with earthworms all the time. One bichir will be trying to eat a big earthworm whole and another bichir will come and try and take it from them. It usually results in a deathroll by one or both bichirs and usually they end up splitting it.