This is actually a really common form of fingerprinting. At one point in time, it could generally tell the website what operating system and CPU architecture you're running on. I know this type of fingerprinting was fixed in Chrome so it always gives the same answers regardless of platform. I think it was also fixed in Firefox and Safari, but I don't follow their releases as closely.

Of course, even though it's probably useless now, things like that hang around because it costs more for trackers to remove the code than it does to keep it in.