Not necessary if you disable JS, which you absolutely should do if you care about privacy while using Tor.
Source: see the Tor Browser docs on why they enable JS by default (though NoScript is installed and can be configured to block all JS, if you know the risks) https://www.torproject.org/docs/faq.html.en#TBBJavaScriptEna...
I know they're trying to serve users that can't be expected to play the whitelisting game, but they really should be stricter here. It's already trivial to differentiate a Tor user from a regular one, they might as well set the most secure defaults possible.