(“underwater offtopic”)
My view on that hasn’t changed since last year…
For the avoidance of doubt, in “beyond the edge” cases a relation (even a route relation) isn’t limited to highway=path. This is an example of something “isn’t really a path” but is part of a route. It’s across open moorland that is also access land so (rarely for England) there are relatively few restrictions about where it’s legal to go.
I suspect that these “underwater paths” are more about tagging for the renderer than anything else, and the mapper there could benefit with a little help with e.g. uMap 