Let's be honest here: Archer's Enterprise is the ultimate retcon, and trying to differenciate "Earth Starfleet" and "Federation Starfleet" is just fans trying to explain it all away. There's no way the ship that paved the way for the Federation, made first contact with Andorians, Romulans and countless others and saved the Earth from destruction wouldn't have come up in conversation in prior Treks or on those "legacy walls" on the -D and -E had Star Trek been some epic plan rather than something made up as they went along.