Google is incentivized to do “privacy theatre” and make sure your incognito session doesn’t show up as related to you even if the back-end systems have a clear association.
I don’t know the facts of Google’s systems either way, but I do know that absence of a visible join is not conclusive evidence that there is none.
It would take a determined and malicious employee to subvert these controls and possibly require multiple employees to get by code reviews to do such.
That said, I can appreciate the skepticism an outsider might have about such claims.
But, I also disagree that Google is incentivized to do "privacy theater" as you call it. For one, many already assume the worst of Google and also such theater could open them up to major lawsuits.
One could make the case that a company like Apple has invested a lot more effort in "privacy theater".
That doesn't mean cookies or logs are joined, and the targeting is always anonymous, so it is less precise than when using the cookie ids.
Eh? There is no chance of this. What leads you to this conclusion?
Is it possible? Sure. A lot of things are possible. Is it inevitable? Far from it.
But that isn't quite the narrow framing you used.