Can somebody explain the technical accomplishment here? What's new about this? Github already hosts source. What do they mean by "package"? Is it just source? I don't get it.
For npm, you might publish your source 1:1 if you have a very vanilla setup, but a typical package in npm contains a built version of the code while the repo contains source, documentation, tooling, etc.
Package versions are also created explicitly and tend to contain many changes, whereas repos are commit/branch based.
Another reason would be having a few private packages and not wanting to manage an entire npm account for them.