Is the Firefox Cookie AutoDelete extension worthwhile?

I am trying to cut down the number of extensions I’m using. I currently have Cookie AutoDelete set to auto-delete cookies when a tab is closed; I rarely shut down my browser so the standard option to delete cookies when Firefox is closed doesn’t really seem ideal.

Is this actually giving me any privacy benefits? 4.1 Extensions · arkenfox/user.js Wiki · GitHub says in the “Don’t bother” section:

Cookie extensions

Sanitizing in-session is a false sense of privacy. They do nothing for IP tracking. Even Tor Browser does not sanitize in-session e.g. when you request a new circuit. A new ID requires both full sanitizing and a new IP. The same applies to Firefox

Can someone explain to me why sanitizing in-session gives a false sense of privacy? I can see that it’s not ideal to delete cookies while retaining the same IP address, but doesn’t this at least create some uncertainty on the part of the site trying to track me whether or not I am the same user that visited earlier? (Let’s assume I’m using a VPN which means my IP address is shared with a reasonable number of other users.)