Fair enough - but malicious or not, it does cause issues and builds barriers to inclusion.
Talking about subsections is not about competition. It's about unhealthy arrangement that, again, can easily be used to exclude people. It just doesn't make sense to divide it this way.
Intersectionality talks about many issues, and one of them, part of it, is sexism. So, putting it under umbrella of feminism is like putting animals under the umbrella of bees.
My experience interacting with men's liberation is mostly just men going 100% into misandric narrative that men are to blame for anything and everything. As one person underscored it under one such post, "if a woman struggles - it's society's fault. If a man struggles - it's a man's fault". There's no room there for not blaming men for the discrimination they receive.