don't put it on Twitter if you don't want people seeing it and possibly talking shit. it's not between them anymore. social media has fucked people's brains, main character syndrome.
I would like to point out that actors are usually contractually obligated to maintain a specific appearance. Stamos may literally have not been able to shave his head in solidarity, so while seemingly noncommittal I think there could be more to the gesture. As you say, Dave is the only authority on the matter either way.