This frees Kurtzman up to manage the franchise and prepare further ongoing projects. This is almost certainly based on Chabon's idea's, the show I mean, so giving him control of it is going to keep it coherent and avoid some of the difficulties that Discovery had to work from, I suspect.
That Short Trek (with Spock and Number one) is called “Chaos Theory”. The press release says Chabon wrote "the Star Trek: Short Treks episode Calypso and Q&A among others." It says episode (referring to Calypso), not episodes. So sounds like Q&A is some other project and not a Short Trek.
Some people seem to be taking this news as some kind of demotion for Kurtzman. I don’t think Kurtzman is interested in being the showrunner for any of these shows. He has a more interesting job of being the boss of the showrunners. He took over as Discovery showrunner in an emergency situation. Even there he hired James Duff to help him. And later hired Michelle Paradise as co-showrunner. She may become the sole showrunner eventually.
I'm confused by the celebrating as well. Kurtzman seems more interested in managing a sprawling franchise, not micro-managing a writers' room. He seems to be in control.