If IP address X does a query, then a moment later the same IP does the same query but just doesn't send any cookies, I am pretty sure Google knows it's the same person.
I have nothing to hide, but I think the age when incognito and privacy options started being celebrated by the browsers was the worst period for me as a web obsessed teenager. Mozilla would have spent some energy highlighting in simple ways how the private mode is a gimmick that has uses but does not protect web privacy. In fact web privacy is not attainable for this and that reasons.
I blame myself for being stupid for believing that the web was about helping people reach progress through minimal harm. Sigh. Innocence !
If IP address X does a query, then a moment later the same IP does the same query but just doesn't send any cookies, I am pretty sure Google knows it's the same person.