I hate to tell you this but i have seen that pic a few times over the years and I actually never noticed. And now that i cant not see it (thank you very much) i actually dont fucking care why.
I'm the same way. I've seen that picture countless of times over the years but never did it even dawn on me to focus on his butt hole. Just in awe of the calves, back, and arms. But I know on this board many like to focus on another man's ass and crotch.
And, of course, it's not a hole in his posing trunks. It's a shadow. But, hey, I don't want to ruin someone's fantasy.