ron Kind of. Sometimes they check for the number of update downloads to get an idea of how many devices there are and how many of each device.
Of course people can have multiple devices, so it's not possible to count "users," just devices. And these estimates obviously can be affected by people who don't update, wait a very long time to update, sideload, devices that lose connectivity and try again, and probably some other things I can't think of right now. No unique identifiers are sent to the update servers, so it's not possible to get a real accurate number, just an estimate.