I have a feeling that version 1.0 will come to GFN. But perhaps Larian is a bit reluctant to bring Early Access to it because so many patches/updates etc will happen in that period.
GFN might fall behind giving people a different experience. I don't know though, just thinking out loud

GFN streams the game from steam so it would be up to date with the steam version which is the fastest to update
they are very quick with updating games as well from my experience
the only thing i could think of that is holding back GFN access is some exclusivity deal made with Stadia which would really suck since Stadia is only available to a few countries which i am not from :c