Did you note how often you and others now use the word ‘route’ in these cases? It kind of converges with my thoughts from the threads you started last year: actually, a path is a kind of route and not the reverse.
Consider this: all physical ways are aimed at allowing people to move from one place to another, and they have in common to be visible, thus allowing users to decide where to go. They are a particular kind of routable objects, others being e.g. free routing across a pedestrian areas, series of cairns in a rocky area, skitouring slopes between two passes, a ferry route, etc. All routable, none except ‘highways’ visible as a linear trace on the ground.
Therefore, rather than reusing the highway primary keyword and adding a secondary keyword to state that actually it is not a highway of any kind, I would say that we need a new primary keyword that encompasses highways as special cases… and this thread suggests that route might be a good candidate.
See: we already have various special cases handled as route=* , and it does not break any existing semantics. We could have route=cairns, route=free (with just two points), route=scramble, route=climbing, etc. Generalizing the use of route would rather consolidate the semantics of the whole. We would just have to imagine that all highways have an implicit route=highway tag. And the same goes for relations: we just have to say that routes can be made of routes, which is already true actually.