It seems they really want to move away from the irc protocol in the long run. I don’t think everyone there is worried about sticking to irc compliance. You have to understand irc is getting old and even with ircv3 it’s not all implemented and/or complete. Now websockets “they’re finally doing them YAY!” they have a similar working method with “messages/events” but can be coded on an app by app basis and has no standard for a chat. I see whispers as being the “private msg” in this new world.
Even PRIVMSG for channels seems weird now with twitch since justinfan### isn’t shown in the list. It’s not so much a “private channel ‘only users who have joined receives msgs’” any more. It’s a kin to saying your walkie talkies are a private convo. I can only hope they’ve chosen good names for client/server messages with websockets instead of just re-using PRIVMSG as well.