Using “server” instead of “instance” is misleading. An instance could use many servers behind the scenes. It may be more appropriate to simply call it a “domain” instead, cause that’s kinda all it is. But instance is also well-understood.
If you really wanted to unify the terminology, you would call communities and magazines “groups”, as this is what they are called in ActivityPub. It is a group of all the people following the community.
But I don’t think terminology unification is a goal in itself. Different clients and implementations can use different terminology and that’s a good thing. There’s no need to force anyone to use a certain term. There’s no need to nail down language like that - it is a fluid, evolving thing after all.