Unable to create repository via REST API with dot in parameter repo_slug

The web user interface allows to create repositories with dots in their slug & name, e.g.:
tld.domain.project

The REST API (tested with 2.0) however returns following error when attempting to create a repository with dots in its slug:
Invalid URL slug value. Slugs must be limited to ASCII word characters.

I have tried plain & url-encoded (%2E) dots. Or do you mean [a-Z] by 'ASCII word characters'? But shouldn't the REST API be consistent with the UI?