AFAIK, and I could be wrong, beeper mini registers a new HWID with apple for each phone. Which is why they thought it was unpatchable, at first, as they would need to determine which phone is in fact an iPhone.
There's much more to the validation protocol than just HWID/serial. See https://github.com/JJTech0130/pypush/blob/main/emulated/data... for a list of the data that is pulled from the platform and used for validation. I would assume that Beeper registrations either use data from a pool of real devices, or made-up data that Apple might "permit" (because hackintoshes) but can definitely detect and block at any time.