If you're setting up your browser to blend in, turning off JS, which nobody in the real world actually does, only serves to draw attention to yourself.
That you are on Tor and that you are not using javascript are two unusual things that compound each other in making you uniquely identifiable.
One reason that it is still relevant even though you are already using Tor is that there are many ways to slip up and expose yourself. And when you do, you've paired this additional one in a hundred identifier to yourself. Might as well just use lynx.
It's trivial to distinguish a tor user from a regular user on both ends of the connection. Hiding the fact that you are using tor is not the goal, making yourself indistinguishable from other tor users is the goal.
