Even James Blish, who used the "Earth colony" retcon to explain "Miri" away, doesn't use it in his "Omega Glory" adaptation, in part because there's no way to reconcile it with the age and history of the Omegans.
There was some debate as to exactly how far in the future TOS took place, until TNG put all that to rest...
Yeah, but there was no way it could possibly have been
over ten thousand years in the future. That's how long ago the Omegans had their war, according to the episode.
And besides, can you come up with ANY other explanation as to how Omega IV could have evolved EXACT COPIES of the Constitution, and the US flag, and the terms 'Yankees' and 'Communists'? I highly doubt it. There can be no other explanation - these people are humans. It MUST be true. Now, exactly how humans got from Earth to Omega IV, is of course highly variable. But that must, by definition, have happened.
Star Trek was produced on a tight budget. The only way Roddenberry could convince the network and the studio that it was affordable was by inventing the conceit of "parallel planetary development" -- worlds that developed in ways almost identical to Earth, so that it would be possible to recycle sets, props, costumes, and the like from historical films and shows rather than having to invent completely alien worlds every week. Some episodes, such as "A Piece of the Action," "Patterns of Force," and "The Paradise Syndrome," offered explanations for the parallels. But others just embraced it as a fantasy conceit. There was never any explanation for why "Miri"'s planet was an exact duplicate of Earth in every way, right down to the shape of the continents. There was no explanation for why the people on Landru's planet were wearing 19th-century Earth clothing, living in Earth-styled buildings, and using clocks marked in Arabic numerals. There was no explanation for why the planet in "Bread and Circuses" duplicated Ancient Rome crossed with 20th-century America, right down to its natives speaking and writing 20th-century American English, aside from a passing reference to "Hodgkins' Law of Parallel Planetary Development." Clearly "The Omega Glory" was following the same conceit. There wasn't meant to be a strictly rational explanation. The parallel worlds were a fantasy conceit that enabled the production of a television series on a practical budget.
Keep in mind that "The Omega Glory" was one of the three scripts written for consideration as the second pilot, simultaneously with "Where No Man Has Gone Before" and "Mudd's Women." So this would've probably been conceived by Roddenberry as a way of illustrating his money-saving parallel-worlds concept to the network. Since early episodes like "Miri" and "Return of the Archons" made no attempt to explain their Earth parallels, I wouldn't be surprised if this very early script took the same approach.
I'm not saying for a moment that I think "The Omega Glory" makes sense. I think the whole last act is utterly idiotic. I'm simply saying that, given the conceits of the story as it is told, there's no way the concept of it being an Earth colony could have been included in the shooting script. If that was in any draft, it must've been a very different, early draft.
(And
Mr. Laser Beam, I wasn't accusing you of lying, just wondering if you were making some strange joke.)