It wasn’t retconned, it’s pretty ambiguous. There wouldn’t even be anything for ady to do about that.
the only real Rebels suggestion should be to put the Ghost into the space battle.
It is official cannon that that’s Rex now.
I personally would get a kick out of seeing the Ghost or any nod to rebels in ROTJ:R-but don’t expect it.
Maybe we should all tweet-bomb Temuera Morrison and convince him to appear as Rex in Ady’s Endor pick-up shots haha.