Non-Apple Airtags, including OpenHaystack tags stopped working

[aircable]

I noticed that around May 20 Apple changed how the iCloud location accepts Airtags. OpenHaystack firmware still sends ads and they look like Airtag packets but the cloud now ignores them.
Somehow Apple was able to distinguish between registered Airtags and the cloned ones.
Anyone knows anything more detailed?
Can we get a discussion going how it is possible without changing anything on any Airtag that they can recognize that?
I start: it is the last byte that somehow is a checksum. It was ignored before. Now it isn't?

[N0madical]

I was able to get my OpenHaystack ESP32 board to successfully send packets through the FindMy network, and have them show up in the OpenHaystack app