Hmm I wonder if it's possible to generate fake callbacks to this to mess up the data >:-] A bit like ad nauseam that tries to mess up advertisers' by taking a click on each ad without actually showing it to the user.
This is the right answer. (The Vivaldi browser company too say the same thing in their forums when asked why "phoning home" cannot be completely disabled). It's also a bit frightening because this means Firefox collects enough data to fingerprint and uniquely identify every browser / user.