The penalty for taking a picture of your ballot is on you, not the person asking for the picture, and it's at the time the record is created, not when someone asks for it. So, it's perfectly plausible and defensible for me to say "There was a poll monitor, I couldn't take a ballot selfie, sorry." That is much simpler than saying "Hey, 911, my boss just asked me for my ballot proof."

(The other thing is that photos of ballots have only become a serious threat in the last few years, and at the moment there's not really voter coercion through those photos, as far as we know. If it becomes a problem, I expect a bigger crackdown on it.)