I understand what you are saying. In our project, when a restriction comes from a straightforward, readily available source like a traffic sign visible in Streetside imagery integrated into the OSM iD editor, we normally do not add an extra source:hgv (or similar) tag to the way itself. Instead, we always cite the imagery source in the changeset comment so any mapper can backtrack what the changeset was based on.

While reviewing the existing OSM database, we found that source=sign or source:hgv=sign is used only rarely.