Well, on desktop it worked. So you could do it that way. But on mobile, what you had to do was go to a website like Google, add it as a bookmark, and then edit the bookmark and change the web address from Google to the IPv6 address.
Probably because most people are not accessing routers and web servers through their IPv6 addresses and instead they are using IPv4s like 192.168.1.1. I mean, come on, who does that?
That patch was my only contribution to Firefox, and I didn't research how to update the user-facing changelog. When 122 hits my phone I'll ping the bugs, to notify the 20 nerds who actually care about the problem. Typing IPv4/IPv6 literals is a pretty niche feature on the modern web.
The Snap is by Ubuntu (and presumably will still be the way Firefox is installed by default on Ubuntu). I think that this is for people who'd prefer not to use the Snap, allowing them to install the .deb directly from the source.