It's like clinching, some gyms you do it at the start of training but most of them do it at the end, right? My gym we do it at the start, which is cool and everything. The upsides are evident. But kinda prefer doing it at the end, after pads, after bag work etc, when you're damn well exhausted. Because that's how it will be in the fight, clinching when you already tired. Which one helps you learn more, when fresh or when tired? Honestly don't know. Feels pretty much same same personally. Just prefer clinching when tired - also the body feels more loose and supple.