If the issue is on the collection side, what technical mechanism does Google have for identifying incognito traffic? There's already a game of whack-a-mole being played because news sites are detecting if you're in incognito mode, but that's in JS, so the access logs were already collected, and the the hacks for detecting incognito are slowly getting fixed, so it's not a viable solution.

DNT is a header, but it's a preference and not legally binding.

The only thing Google did that was "wrong" is that incognito gave uses the impression that they weren't being tracked externally, when in reality the only thing it does is not save your history and start with no cookies.