Matt Pagan:
A common request we see on the help desk is from users asking why they can't connect to some hidden service site. The reason is almost always that the site is down. However the message users see is
Unable to connect
Firefox can't establish a connection to the server at abcdefgh23456789.onion.
This adds to the confusion users feel, as many don't understand why they see the word "Firefox" instead of "Tor Browser".
In fact, any time during the user experience when users see the word "Firefox", genuine confusion seems to arise.
I had reported the problem as #10864: https://bugs.torproject.org/10864