“The functionality segmentation is unfortunate… so we’re going to segment the functionality even harder.”
What they actually think is unfortunate is that a standard interoperable protocol is still allowed to access the platform now that they’ve achieved market dominance. They also think it’s unfortunate that people might object to its removal.
This “functionality segmentation” nonsensical low-effort gaslighting of a justification (also noted by @DevMcGee as such) is adequate to prevent the sort of Streisand-effect Twitter had when trying to squelch Mastadon/Nostr crosslinking or that Slack had when they shut off their IRC bridge, because it sounds plausible to non-developers who don’t understand the details.
They don’t think the developers will coordinate, either.
Twitch has done something much smarter than Twitter or Slack in that they’ve frog-boiled developers for years with a progressive series of tiny incremental breakages and arbitrary incompatibilities (breaking +o in favor of nonstandard IRCv3 tags, PRIVMSG in favor of .w, etc.) that aren’t worth the coordination effort to fight in part. The sanest developers at any given time see this stuff and leave, and, by a process of evaporative cooling, the remaning developer pool becomes more and more credulous and masochistic. This has been allowed to happen for so long that there will be no compatibility left to lose and no real objection made in the final (as @prod observes) forced migration from streaming user message events over a socket to streaming them over a websocket.
Welcome to the Bezos land of Embrace, Extend, and Extinguish. The same place they let you use x509 authentication for AWS services so long as you don’t try to use an external certificate authority. Your infrastructure can check in but it can’t check out.