Probably most Julia packages could have better error messages. A lot of Julia devs work on many packages and/or base and have very little spare time. Docs and good errors, while important, can often be put second to writing features and fixing bugs.
Well-written PRs improving errors like you are here would probably be appreciated pretty much anywhere.
It may be a good idea to benchmark all your error message fixes, because string interpolation code can slow down hot paths some cases.