I wouldn't call it selfish. They want tools for more granular control on their instance. That's perfectly fine. If they limit who can post or comment based on the instance they are from. The other instances are perfectly free to limit their users as well in response or for their own arbitrary reasons.
There seems to be a distinct lack of controls across lemmy as a whole. The only option for them is all or nothing at the moment.
I think the big take away is for users to think about what instance they create their accounts and communities on.