In Vietnam, they mostly use the controversial service=alley for motorcycle paths that are too narrow for cars, along with a mix of highway=residential + motorcar=no + motorcycle=yes. I think both approaches are off, and as you know, it’s been discussed in detail here.
This is intended for narrow paths used mainly or exclusively by motorcycles. If a typical 4-wheel cars can access the path, it would fall under some other minor road classification.
I’m not sure what you’re referring to with highway=road. That tag is reserved for unsurveyed/unknown ways and could represent anything from a motorway to a sidewalk. highway=path is commonly used for hiking trails, so I’m confused about the comparison you’re making with highway=road.
I was simply drawing an analogy that the paved vs unpaved (“built”) distinction shouldn’t be used to determine highway classification. In Vietnam, there are many unpaved roads connecting villages that are tagged as highway=track, but they should really be tagged as highway=unclassified or highway=tertiary.