Either they had access previously, before Google revoked things, or they have used other methods to either create their own personal keys or (potentially bad) spoofing Gnome’s access..
I had one such pre-existing setup that worked, but lost it when I did a clean install. Luckily, I had previously set up a personal key in the past for Rclone to access my gdrive, so I used that.
It has nothing to do with your system, but Google’s decision, and no one doing the work of satisfying their requirements, jumping through their hoops, and invoking the proper incantations.