I would too, but I doubt a young and hungry player who's in good form is going to willingly turn their back on their country just because their manager's a shithead. Having said that, Ben White did something similar with Southgate's England so... maybe if Gravenberch gets totally established as a midfield fixture here... maybe he'll think "I can wait out Koeman getting the sack."
I doubt it though with so many Dutch players and staff around though, I think they'll be keen on him playing for the national team if he's playing as well as he's played the last 3 matches.