"Google uses IPs to track you" has been theorized since 2010 or maybe even before, but I've never seen any study or evidence that it actually does so. So, so much of the internet is built on NAT, shared IP space, and short-lived IP addresses that it really doesn't seem like there is any ROI in having engineers keep their IP correlation tech in service and tracking its efficacy.
Imagine two people live in the same residence. One is extremely privacy conscious, doesn’t even have a Google account, and the other doesn’t even run an ad blocker. Both have the same phones on the same OS version, and for sake of argument, both are on the same ipv4.
Does this mean that, if the privacy conscious person opens a private browsing session on their phone and visits some websites, they start getting ads their roommate should be getting? At what point would Google know “this is the same person, show their targeted ads”?
/s point taken. :)
Tor Browser in Whonix in a Qubes VM is recommended when you need reasonable privacy while interacting with services purpose built to track users.