I think its more that there was an unwillingness to make the distinction between United Earth Starfleet and Federation Starfleet. That goes back to establishing and fleshing out the concept of United Earth within Trek. As it went from being a part of the declaration in the New United Nations of the 2030s, to being adopted for use for the space probe agency a few years after First Contact, to being abolished as a concept altogether a decade later due to the post-atomic horror, to coming back into favour as a concept by the time Starfleet was founded in the 2130s, to being an actual political entity by the time the NX-01 launched. United Earth just was not at the forefront as it should have been for the series. Everything was too centralized with Starfleet. Various United Earth branches working together should have been the main idea. Even using UES – United Earth Ship – as a registry prefix could have helped differentiate the time period altogether from the rest of Trek and clearly establish what the show was about.