Tor Browser 5.5 introduces protection against fingerprinting but due to an oversight it is not enabled in Tails 2.0. However, this is not so bad for Tails users since each Tails system has the same fonts installed, and hence will look identical, so this only means that it's easy to distinguish whether a user of Tor Browser 5.5 uses Tails or not. That is already easy given that Tails has the AdBlock Plus extension enabled, unlike the normal Tor Browser.
I wonder why they opted to preload it with AdBlock Plus instead of uBlock Origin. I'm sure gorhill would certainly give his blessing, and by all measurements it is just as effective with way less overhead.
Heck, they could go one step further and preload it with a uBlock Origin profile on a paranoid mode that proactively disables all JavaScript (last I remember using Tor I had to manually disable Javascript in the Firefox config).