I'm in that camp of has a dating app installed but have no partner so the is-my-partner-cheating admittedly doesn't resonate with me. I've had to do some of this fingerprinting myself before for non-data-selling reasons so a lot of the system-level statistics didn't quite impress me [1], but that one was a gut-punch when I saw it pop up. It makes me wonder what apps out there have leveraged that as a signal for ads or other behavior modifications to exploit my search for a partner -- without at least having to spend a few pennies querying a data broker!

It makes sense that there's some discovery mechanism - since Google loves to use it to prefer Chrome, GMail, etc when you're in one of their apps. I wish that there were more restrictions though where you only get implicit permission to query from apps that have the same developer ID. Maybe a mutual allowlist that has to be formed, or some sort of privileged intent where you at least have to tell Apple what's going on and that gives them some contractual right to sanction you if you're using it for nefarious purposes instead.

[1] excluding the clipboard copy count, that was novel!