Alex the Awesome, and independent city-states? I doubt in some remote dictatorial or oligarchal outpost, the government there would have been described as "Alexander-the-Great-ian".
But I agree that perhaps "dictatorship" could be sometimes replaced with Fifedom or something implying where the taxes go, and who shows up and stays, if you need Imperial military help.
I get it, that various local protectorates are actually described by their local government type, and not where the basking tithes go. It's just brutal honesty and a tip of the crown to how local systems are run.
American Hippies in the Viet Nam era: No spreading "democracy" at the point of a gun!! Don't go around overthrowing regimes!! Budding corporatism is the great evil, you're transparent!!
American Hippies in this era: We won't fight ISIS on the ground in Syria unless we can overthrow the current government!! They're evil!!
I'm not taking sides, just pointing out how things change. And, Yes I have had both those opinions clearly expressed to me by noble warriors then and now, I'm not supposing anything.
I think the Empire is simply being flexible, while flexing its (significant) differences from the Federalis. Yeah, our control extends to various systems in various states of isolation.
Edit: Also, in the late 70's it was common to believe that the crushing weight of bureaucracy did indeed squish the Roman Empire. I don't know if that opinion is still held. It's possible that the Empire doesn't burden itself with massive and unnecessary bureaucracy.