Are they, really?
The less debatable point is arguing that making CICD pipelines slightly faster, but this feels like an appeal to microoptimization. Any free tier CICD system out there let's you do a single npm install and move these dependencies as far as you'd like into the pipeline as artifacts. Is a git checkout really faster that a npm install?
For example, is adding a npm dependency really invisible if you already track package.json and even package-lock.json? Those files show up in diffs, and it's hard to miss them.
Also, if the goal is to get replicated builds, isn't this handled by pinning versions and tracking package-lock?
The left_pad example is particularly ridiculous as I highly doubt that a company like Google, like any company that cares about auditing and vending dependencies, does not run its own npm proxy with cherry-picked packages.