Now we're talking.
For normal gym purposes, we do have a load of things for all sorts of little rules (or even big rules) for things we do- full ROM, don't cheat in various ways etc. But elite athletes frequently do it in ways that ignore those rules, because that is what they need to do. It's possible that he's doing curls for injury prevention, and he and his team figure that they get more benefit going as heavy as possible and non-full ROM than they do being super strict. Or maybe they do some more strict and some more like this. I'd guess that for Louis-Philippe Jean's video, they figure power curls are more similar to the movements that really stress the biceps in strongman.
But I guess the main point is this: curls are awesome.