It has been played extensively in every world championship when the win is needed. (white or black) And the top 30,000 players (including engines) should be followed for the latest developments in the Grob for what they improved upon to keep the opening at the very top of their playlist...incredible stuff!!
Is the Grob playable?
To be honest I'm quite shocked that chess hasn't been declared solved for a win for White and Black due to the g-pawn .... amazing. Someone really needs to discuss the false narrative we have been digesting from FIDE don't you agree?

It does not matter if it loses by force or not, or even how much worse white is after "perfect" play from both sides.
Playing like that is a bad habbit, which won't help you improve at chess- quite the opposite.
WHAT
(sorry all caps)

Openings that are objectively bad have some point when the positions are difficult, but with the grob white is the one suffering, and it takes very little time for black to learn how to play the opening, so I don't understand why white would choose to play it.
I assume it's mostly chosen by beginners who can't tell the difference, and by good players who want to show disrespect.
Each opening is ok, if you know how to play it correctly.