Yeah I hate this. I've never had a game that can be played in any way until the full download is complete. Why they even show it still I don't know. I guess devs didnt adopt it like they should have but then at least ms should remove it as being shown from the games that don't adopt it.
I definitely see value in it but agree it doesn't usually seem to have been implemented properly in most cases.
I would like this feature on PlayStation as being able to strip out multiplayer for RDR2 or other hefty games which I'm never going to play would allow me to keep more games installed.