I get what you are saying, but have to disagree with how it plays out in reality.
First, you are citing one of a few exceptions to make an point for the majority. Mika is in better than average shape, though not "perfect" shape at all. If that's perfect shape, then I'm surrounded by gods. But seriously, he's only one of a few players that are in decent shape. The majority of winning pro players are not in shape at all. Second, being in shape is not the same as being an athlete.
Being out of shape can hurt, being in shape can help,
but being in shape is not a necessity to win at pool even over a long haul. Plenty of mediocre (or worse) shape players play long tournaments and survive to finish well. There are world-class players that have never been in shape their entire lives. For some, the closest they have come to working out is lifting a cue stick (or lifting a doughnut from a napkin to their mouth). Kind of like this...
Great Athletes
The game is about skill/knowledge and mental stamina... And being physically capable of executing (which being in shape is certainly part of). But the kind of physical stamina needed to play pool is not the same as needed to run 10 miles. You can be in average physical shape and still rock the house over a multi-day tournament.
But I'll admit, I just made this reply so I could post that video link