Google is being sued for tracking users in Incognito Mode
https://www.xda-developers.com/google-is-being-sued-for-tracking-users-in-incognito-mode/
> The reason? Google still picks up some of your personal information, such as shopping habits and other sensitive data, even when you’re in incognito mode. How do they do it? Through services such as Google Ad Manager, Google Analytics, etc. This collected information is not directly tied to the user, but it could potentially be used to identify a user if the information matches previous habits.
うーん……もうちょっと具体的に技術的詳細がわからないと判断しかねるな