I would expect a directory to be crated automatically, because if you want to mount a drive the source needs to exist in advance. The $user variable should only help you to ease the setup by covering everything with one single configuration entry instead of creating mount configuration for each user separately.
IIRC the path is expected to exist when using substitution variables. I don’t recall any special handling post-substitution in the path. The documentation could be clearer about this.
P.S. If so inclined, you can fork the docs on GitHub and edit that documentation page to propose a change (in a pull request). Once you’ve forked the docs once, it’ll also be easier to simply click “Edit on GitHub” in the upper right if you come across other areas of the docs (in the future) where you want to propose clarifying something too.
