Delta Vega is obviously supposed to be a completely different location
A minor nuance here, but perhaps relevant to the thread's premise...
"Delta Vega" is rather unlikely to be the name of a location.
After all, there's no constellation Vega in existence in the real world, and we have no direct evidence that there would be "additional", fictional constellations in existence in the Trek universe, either. So Delta Vega cannot be the fourth-brightest star in the nonexistent Vega constellation, nor the only planet circling that nonexistent star in that nonexistent constellation. And elsewhere in Trek it is unheard of that "Delta" would denote something like the fourth
planet of the star "Vega" (which does exist) - planets get Roman numbers, not Greek letters. Add to this that the Delta Vega in TOS was supposed to be at the fringes of the galaxy, while the real Vega sits right next to Earth...
Now, the TOS episode says this about Delta Vega:
Spock: "There's a planet a few light days away from here. Delta Vega. It has a lithium cracking station."
So the name of the planet is Delta Vega, rather unambiguously. But given the above argument, it's likely to be a proper name, not a systematic one - that is, unrelated to the star Vega, beyond the way
USS Vega or Chevrolet Vega relates to the star, and unrelated to the location of the planet.
The planet in TOS has only a single attribute attractive to the UFP or mankind: it's rich in minerals. There are no inhabitants, but there's a UFP mining presence there. We know of another place exactly like that: Dytallix B of TNG "Conspiracy" fame. And we also happen to know that this place got its name from the Dytallix company that owned/operated the apparently automated mine. It's not a giant leap from there to saying that Delta Vega follows the same pattern of naming: it's the fourth planet belonging to a commercial or government interest named Vega.
From there it would seem to more or less logically follow that the TOS universe contains places called Alpha Vega, Beta Vega and Gamma Vega, too, and perhaps more. Perhaps in STXIverse, Beta and Delta simply swapped names? The place Scotty and his little helper supervised did appear quite automated yet also extensive and vaguely industrial, in TOS Delta Vega style, even if it was only generically referred to as a "Starfleet outpost" by the lifepod's computer.
As said, just a nuance. But it stands to reason that a place named "Delta Vega" would be differently positioned in slightly different timelines, as the name would be randomly rather than systematically assigned.
Timo Saloniemi