I dont really understand the issue with browser fingerprinting. Yes in theory it can uniquely identify you but only if your browser fingerprint never changes.
Everytime I go to one of these "are you unique?" websites, I am a new guy to them.
Tie that all together and it may very well be possible to tie an upload using the Tor network to a particular user visiting some random website at a later date.
You're leaking bits all the time and not all that many of them are required to uniquely identify you.
See https://33bits.org/ for an easy to consume introduction.