Not trying to come up with far-fetched theories but we all know this fandom cares/comments on his upper body a lot. What if he wasn't as fit/big as he tends to be in movies and was in his "skinny phase" and he didn't want to take a pic of his arm so people don't go on and on about how he's not as fit as they picture him? Men have some pressure to look a certain way as well. And there's enough reasons to think he's vaccinated so he didn't really need to post a pic of him taking the shot.
Tbh, I just feel he didn't post a proof because he just didn't want to. He didn't post he voted, but we damn well know he voted last year.
I think, just like some previous anon said, he has made his best trying to inform people through ASP. He wants people to know what's up with the vaccine and Covid, why it's important, and get a conclusion and decision by themselves and not because a famous celeb they follow posted about it.
We tend to forget most of his politics/social posts are an insight to his beliefs and thoughts (just like most people on social media) and not because he wants to encourage/make others think the same way he does
