Roddenberry used to pontificate about Starfleet being quasi-military even back in the seventies, but I do think some of that was only in retrospect. For example, at conventions he used to talk about how he never believed Starfleet would have had an 'enlisted' class, or that by the 23rd century everybody on ship would share the same kind of crew quarters rather than pairing up in bunks like in a barracks. That kind of thing.
But in practical terms, TOS only sorta-kinda implied this stuff (the Meyer/Bennet movies ignored it completely). Phase II was in many ways Roddeberry's attempt to conceptually realign TOS with what his beliefs then were, and when that didn't happen he simply emigrated that through to TNG.
