That's one way to fix supply chain vulnerabilities.
More seriously, keeping a local cache of external npm packages, and a local artifact storage for internal npm packages looks like a wise thing to have done long ago. Might be cheaper in the long run.
Ironically, both Nandu and Verdaccio are implemented in Tyepscript and install via npm.
(Same logic obviously applies to Python packages, Docker images, etc.)
Can't have any vulnerabilities if you don't have a supply chain