You are right about our external data docs, we should probably review them. We actually have an old issue about this… https://github.com/iterative/dvc.org/issues/520 feel free to upvote (like) and/or comment there.
As for the bug you bumped into, please follow https://github.com/iterative/dvc/issues/4144 instead, as the one I opened was found to be a duplicate.
Best