It's part of the short treks, I don't know if all 4 of them tie into Season 2, but a couple of them do. Plus it is set on the USS Discovery, you can just barely make out the ships name.
It's set 1000 years after Discovery. I suppose this qualifies as post-Nemesis, but that's a strange way to look at it.
Is it set on the Discovery, or are they just really lazy with the effects and it's some other Crossfield ship?
Short Trek is currently a spin-off of Discovery. I am hoping in the future they open it up to be any kind of Trek story, but budget limitations probably restricts it to reusing sets and CGI elements from other ongoing shows.
It's not like Star Trek shows have never reused sets. The only limitation I see is CGI for the ships, but even then they must have them all programmed in. So, I don't see this as a barrier.