In my experience in adtech, not only can Google do this pretty accurately, but other third parties as well (e.g. DMPs and the like.) Even if they couldn't make a deterministic association, they have enough data points to make a probabilistic association with high likelihood (ex: "Given all these data points, we're 95% confident that these two people are the same. Therefore we're going to attribute the actions to the same person.")
Now, to qualify my response a bit, this isn't necessarily for security / law enforcement, but mainly for better targeting parameters. Example: frequency capping of ads (buyer specifies that you only see an ad X number of times in a given time period) or more relevant targeting (you don't see completely different ads in different browsers as if you're from two non-overlapping demographic groups.)
Deterministic = I specifically say I'm person X and am logged-in. Probabilistic = I am not logged-in on this browser, but am on the same computer, same IP, and am logged-in on a separate browser at the exact same time under name X. Therefore I'm very likely person X.
Nothing coming from PV can ever again be taken with a single grain of salt.
It's _very_ frustrating when people immediately discredit someone or something because they don't agree with them, even if they don't have the full story.
Project Veritas does some good work, even if they're blasted in popular culture/mainstream media for being 'biased', 'alt-right', 'etc'. I bet you the downvotes you're getting are just because you mentioned Project Veritas.
They have some very out-landish views, but when they actually put people on the street or go undercover, they've revealed dirt on a lot of companies and people.
It's shocking to me to see society go from "let's look at ALL sides of the coin, no matter how egregiously offensive they are to me" to "fuck 'em, they're trash media, they suck, they shill and are racist, alt-right losers and I'm not going to look at anything they post because in my mind everything they do is bad!"
I don't even go to Project Veritas outside of what I hear in the media, but I still give it a fair look and make my own opinion.
We can talk about tech surveillance without playing into the modern fascist agenda.
Even a single one of these incidents is enough to completely throw every thing you've done and said into doubt, let alone the half a dozen that PV has behind it. There is absolutely no way you can take anything they say or do serious after they've been caught times and times again lying and misleading.
It has absolutely nothing to do with how outlanding their views are, and everything to do with the fact that what they say or do cannot be trusted. I used to in the beginning, but they are way past being given a "fair look".
[0] https://www.bbc.com/news/world-us-canada-42150322
[1] https://www.theverge.com/interface/2019/6/27/18760463/projec...