Phase 4:
"Characters created during this phase will be carried over to the official release"

Needs some clarification, is it just the character appearance and name? Or is it also the progress you make?

There is some confusion in the wording.
What's confusing about this? If it was just your name/apperance, it would specifically say that. Of course your progress will be part of what's carried over.

So I am leaning towards a situation where only character appearance is saved, otherwise a benefit like early access would serve no purpose? Since phase 4 would be considered "early access" if all character progress is saved.
you're leaning incorrectly, and i'm not sure what you're basing it on. "early access" means "Play the launch version of the game a little before everyone else." That's all it means, it doesn't mean anything more or less.

There's nothing ambiguous about the statements.