I am raising both as a bug and feature. A bug because:
if the workflow data folder contains data and
the reset workflow option during export or upload to the Hub is checked
that data still remains
A feature to add a dedicated option to allow selectively purging the workflow data folder for:
Export / Upload of a single workflow
Export of the entire Workspace
In case you need a test workflow, I discovered this while developing my workflow which allows to back & transfer workflows and entire workspaces I shared for the community.