I wish it had a way to integrate with the Find My app instead of having to go through their own (wonky) process to retrieve locations. The chinese clones can do it (even with their own branding), so it must be possible somehow.
The keys broadcasted by the devices themselves in 'lost' mode (i.e. not in 2 way contact with the owner's device) are arbitrary and completely opaque, Apple doesn't have any way of tying them to an ID or device or developer. This is how the proposed project here works - these keys will always find their way to the apple server.
It seems like the knockoff ones have just hijacked a legit key for the pairing process. This means if Apple desires and finds out the key, it can probably remove all devices from all accounts - although the devices themselves will keep on broadcasting and their locations could be accessed in the above janky way. I wonder too if the original key owner might get a large bill for per-device royalties if/when Apple searches it's DB for a count of 'devices-added-to-an-apple-id-signed-by-this-key'...
Apple officially supports third party trackers, who’s manufactures are issued, by apple as a part of their MFI programs, keys with which these third party devices must use to sign their pairing requests to the users apple account.
Perhaps these $5 devices do indeed include legitimate keys from apple to use from this, perhaps they have copied one from another device.