Google still lets you do some things without logging in but that doesn’t mean that they don’t build profiles or try to link them with other activity sources. Most of their revenue comes from advertisers paying for targeting.
The paranoia but also the naïveté of internet tracking is a bit of a rare combination I think. Shadow profiles have been a thing for 15 years or more and they have only gotten more sophisticated. Browser fingerprints are surprisingly unique. Unless this guy is rotating machines / vpns / using qubes / etc Google can very likely pinpoint within a degree of certainly which searches are theirs.
The paranoia but also the naïveté of internet tracking is a bit of a rare combination I think. Shadow profiles have been a thing for 15 years or more and they have only gotten more sophisticated. Browser fingerprints are surprisingly unique. Unless this guy is rotating machines / vpns / using qubes / etc Google can very likely pinpoint within a degree of certainly which searches are theirs.