This is not necessarily about uniquely tracking users. This is likely about telling automation from manual traffic to login. Credential stuffing is a large eno

This is not necessarily about uniquely tracking users. This is likely about telling automation from manual traffic to login. Credential stuffing is a large enough problem for account takeover and the cost to a user of losing their gmail account so high that at some point a team has to make tradeoffs about what can and cannot be used to log in. edit: am Googler, not working on this area. Have background in account takeover/browser fingerprinting.