What Google can do and what they choose to do are two different things.

I don't doubt one bit that they have people capable and probably even willing to get the crypto right.

I _strongly_ doubt they have the corporate will or motivation to actually put it into production. I'd go so far as to say "getting it right" is antithetical to their (enormously profitable and deeply entrenched) business model.

I don't know about that. Measuring ad impact is extremely valuable. What is interesting to me is the obvious bias of being the seller of ads as well as the impact measurement provider.. fox guarding the henhouse and all

If they sold it to Mastercard as double blind I personally would trust them on it. Lying to consumers seems to turn out fine but lying to large corporations I would bet gets expensive and my experience is that a large org will bend over backwards to meet the letter (if not the spirit) of what they say.