First off, cool your jets; you're being kinda rude for no reason here. Just because we disagree doesn't mean either of us is an idiot.
My point is just that you still develop features specifically for your admin-privileged users right? That's the only thing I'm trying to say by calling admins users, that they still belong to the bucket of people you consider when adding features to your software, even if they are only admin-facing features. You're right that it's just a semantic difference, so let me rephrase using your terminology then;
Admins of the software may want to create and promote their own private sites using the lemmy software that federate with only a subset of other lemmy instances. For instance, a network of 'academic' lemmy instances run by universities -- with high moderation requirements -- that do not federate with the 'popular' fedeverse.
In that sense federation is a feature, to admins.
I'm also not 100% sold on it not mattering to end-users. Like I'm a user by your metric, and I like that Kbin can de-federate from extremist instances or instances run by corporations like Meta, and will likely move homes if it doesn't and I start seeing too much content from those instances. It's a feature I specifically appreciate about this platform.