Probably a subtle push to sell the cloud-hosted Enterprise version. I bet the on-prem Enterprise will slowly stop getting all the latest-and-greatest features. Producing and supporting the on-prem version has extra costs, but probably doesn't bring in enough (extra) revenue to justify working on it as much.
> GitHub Actions: Artifacts v4 available in GitHub Enterprise Server
So they're deprecating Artifacts V3 next week, and now announced they won't upgrade Enterprise Server to v4?