No merit to your assumptions. Rock playing surfaces have no effect on tapping balls to stay in place, but cloth does. The finished surface of the slate, granite, or marble surface is never, ever...ever going to "wear out, or change" no matter how much it's played or, or for how many years the tables in use. Granite my be a cost choice over using slate from Brazil, but it certainly is not going to provide a better table.
I thought that some kinds of slate in dry weather would split into layers (like puff pastry) and bubble up in places.