[figgyc]

I think one thing overlooked is that Google's supposed rationale for providing this service is effectively because they suppose that their plans to "more aggressively block fingerprinting" will leave advertisers with no other choice.

Personally I find this highly unlikely. The very nature of fingerprinting makes it difficult to prevent without some pretty severe compromises, and it wouldn't surprise me if advertisers enter an arms race with Google instead of caving in.

Of course the economic strategy for Google to avoid that is to reduce the price/limits of this service to so low that this isn't worth doing, but if the effort Google puts into preventing fingerprinting is insufficent then this would lead to a "worst of both worlds" situation - Google gets to pseudonymously track the internet with their "privacy sandbox", and nefarious trackers/advertisers can combine that with fingerprinting to create an even more reliable picture of who's who on the Internet.

FYI, this[0] appears to be the explainer of what Privacy Sandbox actually is, and it's quite vague, presumably because the actual implementation details of this would be difficult to determine.

[0] https://github.com/michaelkleber/privacy-model