I don't think the DP walked into
the shot, he was walking through Bale's eye line.
Not that he should necessarily be doing that, either, if he's been told not to, but there is a certain distinction. One really is amateur, the other is just respecting an actor's request.
I've known and worked with plenty of actors who couldn't care less what was going on around them, they could just tune in and get it done. One's not better than the other, mind you, just different preferences amongst artists.