Originally posted by grapplehoeker:

I have never understood why Iron Gate chose to restrict it to Discord.

Discord is the new hot sh*t !!

Joke's asside, the process exist as it requires some dedication from the end-user.
This is likely both to prevent accidental opt-ins and to at least try to push users to actually test it out and report issues rather than just have early updates and try to play on those.

You'd be surprised how many players opted in experimental branches of their games and complained about issues steming from these unstable builds.