Actually it also helps for this.

O standardize how HAL interfaces between the framework and the low level vendor implementation.

So you can update either, as long as the interface contract is respected, it should be transparent. It is of course more work for Google since the framework will need to keep supporting old version of this interface but that's a necessary evolution.

I think the idea is that you can update the HAL portion as well, and the system on top of it can be verified to have not problems with that HAL independently (and you can wait for that or or just update the HAL as available if you think it's important enough).

Since it's semantically versioned, you can theoretically have fairly high assurance of what updates might cause problems and what should purely fix a bug that doesn't affect normal functionality.