Original Star Trek is hard to reconcile with later Trek if you refuse to accept later Trek as being fact (or at least, the most accurate interpretation of that information). For example, it was mentioned on this thread that Star Fleet doesn't refer to an organization, but to a star fleet. However, in later trek, Starfleet is referred to as an organization, and that the original series Enterprise was a part of that organization. Also that the Federation Starfleet has always existed.
I know we try to desperately find explanations to make original Trek fact, but later Trek contradicts it. Its simply that. We know that UESPA is not giving orders to Starfleet by the end of the 23rd Century. We also know that non Federation governments view the Federation as Earth. Earth is the capitol of the Federation, and what we have seen on screen is that humans make up the most of the Starfleet's population. We also know that everything is in English on a Starfleet vessel (although I'm sure panels can display in any language, that doesn't change the fact that signs, like on doors are in english). English isn't an alien language. Its a language from Earth. Where the Federation has all of its government buildings.
So for me, which of course is just my opinion, is I disregard the UESPA references in the first series. It makes no sense to the greater continuity of this universe. Starfleet is the Federations defense agency, and is responsible for all defensive and offensive operations. At the same time Starfleet is a large organization, and performs many peacetime tasks. Like exploration.
Later trek has inserted UESPA into Trek history. So it did exist.