Well, yeah, the feature itself is not a particular accomplishment, really it's been in Firefox for years, you just had to enable it with some about:config-flag.

The big news is them enabling it by default in some fashion (that is when you're in Private Browsing), meaning that all users now have this, not just the 0.1% who understand referrers (and have not forgotten to enable this the last time they installed Firefox).

As a power user who knew about this, you might not particularly care, but for users in general it's great, while it pisses off webpage owners.

Then again, even as a power user it's impossible for you to know about all of these sort of config options, so you might care to use a browser which tries to help its users out while having to keep an eye on not pissing off webpage owners too much, rather than a browser that tries to maximize revenue for webpage owners while trying its best to hide all the ways it infringes privacy from its users.