> I don't use Siri

That's likely true. Unless you were careful to do a lot more than just disabling it, it does use you though, slurping up quite a bit of data.

How?

reference? Proof? How is it slurping data if I have it turned off and don't even use it?

You have to disable the data slurping for each app. The main toggle just governs whether it responds to voice commands. Previous discussion [0].

Separately, the data Siri sends isn't held to the same differential privacy standards as some of Apple's other diagnostics. They just give you a unique ID and yolo it [1]. Unless personalized device behaviors are somehow less identifiable than all the other classes of data subject to deanonymization attacks (demographics, software/hardware version fingerprints, ...), that unique ID is just to be able to pretend to the courts that they tried (give or take Hanlon's razor).

[0] https://news.ycombinator.com/item?id=39927657

[1] https://www.apple.com/legal/privacy/data/en/ask-siri-dictati...