Nonetheless, even if everyone does it, it doesn't mean it should be something that should be encouraged, which is what the commentators seem to be doing.
It's just a part of the game at that level. It's not a big deal. There are always very subtle gamesmanship things going on out there in matches. At that level, these guys feel the slightest edge may give them some sort of advantage. Sometimes they are obvious, sometimes they are very small things that virtually nobody notices. When one of the more obvious things occurs, some people don't like it.