The Tor browser is 100% unique, it makes no attempt to pretend to be anything other than itself. Your anonymity set is other Tor users, not other Firefox users.
The fact that they can detect that you're using the TOR browser configuration isn't that shocking when they also see that you are coming out of a TOR exit node, or the site you are loading is an Onion site. The anonymity comes from looking like every other person who downloaded Tails.
This doesn't contradict anything I said. If you believe you are contradicting what I said, perhaps you could rephrase what you thought my comment was communicating. Otherwise, I will interpret the intent of your reply as adding supporting details.
