Well, Apple has a super weird bug tracker that you can report stuff but you are kept super in the dark - I remember reporting Safari bugs in the early days of WASM and it was zero communication until the bug got fixed.
So I would bet that it was built at NeXT and brought across.
It's in the archive going back to 1999:
https://web.archive.org/web/19991009144258/http://bugreport....
Now, it may be that the Apple bug database is always called Radar, regardless of implementation, like the Dread Pirate Roberts.
The information from the public "tracker" is just forwarded to the internal Radar and that's a one-way street.