Indeed it does not, and I did not mean to imply steepness is a reason for footway/path distinction.
The wiki however does say that highway=footway is intended “for designated footpaths”. The thing from picture above looks at best as informal footpath to me, not a designated one, and I don’t see signs attempting to mark it as designated.
While it is certainly possible that some, ah, logic-deficient municipality indeed didn’t think it over and officially designated this footpath to be used for all pedestrian city traffic (including elderly people, mothers with prams etc), I find it unlikely (and if true, that is indeed something that should be loudly complained about, as I sincerely doubt that it could be used by vast majority of pedestrians – instead it looks like it could be used only by talented parkour athletes)
Making it a path doesn’t even imply anything particular about the way’s extreme slope either.
Indeed it doesn’t, but I don’t see tagging that fits better then most generic path. (as ideas like highway=demanding_path never materialized beyond the basic ideas – if they did, it might fit even better than more generic highway=path).
Only the sac rating does.
Yes, that (sac_scale) was my point (BTW wheelchair=no and smoothness=impassable mentioned before also fit, but not to repeat too much). Depending on local situation I’m not familiar enough with, informal=yes might fit too.
Even then nothing else calls out that this way is not within range of what normal path or footway is like.
I’m not quite sure I parsed this OK.
But to me, if vast majority of pedestrians is physically unable to use some footpath, than it is not really highway=footway. Especially if it is not officially designated to be used by pedestrians.
highway=path on the other hand has “very broad, non-specific meaning”, and e.g. it might require you to use both feet and hands (see highway=scramble thread linked above), or it might even be unpassable for humans without specialized equipment, or it even may be animals-only. Thus, it fits even for such ways (even if, as you correctly note, by itself it does not say anything about how hard it is to use - thus the all other tags to be added are needed).
Does that better clarify what I meant?