Obviously the author should use whatever they want. But...the reasons given aren't in any way compelling.
> If my build process fails, for whatever reason (like an unpublished npm module),
If you were unable to deploy because `left-pad` got unpublished then 1) you've got way more problems than your use of SASS, 2) not using SASS would not have helped you because you're build process is still broken, and 3) you could still run SASS manually.