The fingerprinting potential may well be limited, but it's the principle of the thing: The browser should not provide unnecessary information about its surroundings.

It would be another matter if this was a very useful feature, but I don't think that it is.

Here's one use for it: Ads could sense that they are off-screen and withhold content until the ad is moved back in view. I could easily see screenX/Y being used for that. I mean, I hope not, but how am I going to stop it?