I loaded the site and went through the stuff and it worked fine. Then I turned on my VPN, and it gave me a new ID.
Changing my VPN endpoint and refreshing the page didn’t work, it still knew who I was, but closing the window and quitting the browser before changing the VPN again gave me a third ID.
They seem to know quite a bit about my phone, but it doesn’t seem like there is much that it could differentiate it from another person with the same model of phone.
This was a fun exercise.
I did a private window in Safari on iOS.