Sure there are zillions of chess positions and maybe only 100 billion chess games played so far. But to discount the 100 billion chess games played, especially those games played by the top players makes little sense. The top players while not perfect, know a heck of a lot about chess. And when you get a top player with a top machine you have rather closer to perfect chess without errors than most of you assume.
Suspose your had one million balls each the same size in a bin. You know
some are red and some are blue and some are yellow. But you do not know how many each of the same color. Now suspose you have twenty different people to put their hand deep in the bin and pull out a ball.
It just so happens that all twenty pull out a blue ball. Now is not that some evidence that there are probably more blue balls than any other color? It does not prove there is a erponderance of blue balls but it is an indication that it is likely there are more blue balls than the other two colors.

George, I thought heuristics aren't supposed to be any indication of anything with regard to this question. How then is your subjective perception of chess being drawn so much higher than 33.3...%? I would think it should be extremely close to 33.3...% if you don't think heuristic indications have any relation to reality.
At least TetsuoShima was consistent when he did (ultimately) estimate the chances of each result to be one out of three, as that related to his argument that nothing we currently know about chess can be reasonably used to weigh any of the possibilities as more likely than the others.