You're applying the political science definition of 'federation' and not the computer science definition. They are different. Federation in CompSci terms has to do with networking providers using standardization to interoperate, which is exactly what the fediverse does.
Yeah, someone else already pointed this out to me. All I was aware of (and got from google when checking) was the political definition, so I thought that's all there is to it. I guess this is one of those cases where I should have probably asked ai instead of google because I'm sure I would have been informed of this that way.