Obviously we are each making some guesses as to What Would Happen If...
As it turns out there is an objective way of seeing if 3 significant digits is appropriate. The USTA could verify whether players one hundreth of a point perform any differently, with a few mouse clicks and publish the results. Heck they could likely get the results published in a Journal somewhere.
That information would not be my (or anyone else's) opinion, it would be a statistical fact. All I'm saying is that IMO such a review would reveal that there is no justification for the current system, but you are correct, until the USTA provides the info, we are all, essentially guessing.