Yeah, given how NECA works, what we've gotten is the most logical choices.
- Ultimate Biff that represents his past self in 2 movies, where the bulk of his accessories come from part 2 so sell it as part 2.
- Doc from the past that represents the most significant costume on screen that appears, in some part, in all 3 movies.
- Marty from the first movie in his iconic 80s outfit, the most popular choice.
- Marty from part 2 where parts like legs and torso can be recycled from the Part 1 figure, reduces costs getting a new figure with as little new as possible and also delivering another look.
The Tales from Space Marty is an exclusive, probably limited in production, and likely just something NECA wanted to do for fun.