The association is generally limited to recovery email and phone numbers.

In the case of AdWords, your billing address is also a linking factor.

In the case of Google Cloud, being Owner of the same project or organisation is a linking factor.

In the case of Google Payments, using the same bank details is a linking factor (also applies to GCloud).

Even if that's the case they may change it with some new ML/AI solution in the future. Then run it retroactively on past data.

That's the thing, you have no control over what Google does and little recourse once they do it.