alt Hacker NewsCIs having per-package installs : version ratio > 1 are fundamentally dumb idea in the first place.
In a way, this teaches us that there is something as too much reliability in an ecosystem. Specifically, Github is apparently reliable enough that its occasional outages are insufficient to kill all the companies running these dumb CI setups that redownload packages from the Internet every build - so there's no incentive to reduce waste and improve security globally.
Redownloading and automatically updating to the new version are pretty orthogonal. You can have a solution which caches the packages but would still update to a new version or a solution which redownloads the (verifiably) same package each time. Vendoring libraries stops both but it's the automatic updates which are the biggest risk factor.