I have failed to find a single picture of a person who trains in BJJ who doesnt do this when posing?
The problem has become so acute with some grapplers that they even do it in family pictures, even if they are holding their kids in both arms. Some characters do it with both thumbs even if they risk dropping their kids on the floor.
Would it be considered a sign of weakness to relax the thumb and pose like a regular civilian?
Is the thumb up a counter against the camera's flash?
Perhaps our photographer friend on the forum can provide some insight on this mind boggling issue.
I am right handed and I tend to pose for my photos southpaw with my right thumb up, this confuses the camera man (you know.....just in case he should go for a take down).