An abstraction layer doesn’t prevent Google from seeing the data. Last year the story was that Apple would be running a Google model on their (Apple’s) own server hardware.

This story says the custom model will run on-device and in Apple's Private Cloud Compute. The implication is that Google will not see the data. The "promise" of Private Cloud Compute is that Apple wants it to be trusted like "on-device".

Presumably cutting Google out of getting the data from this is part of why this story first was mentioned last year but is only now sounds close to happening. I think it's the same story/project.

Yes, and that's still the story, as far as I can tell. So an abstraction layer would let them swap out the underlying model