The proposal was rejected, so I don’t think so. Or at least use it alongside highway=path, it’s doubtful that information would ever show up in a renderer.
Yeah that’s something I think about too. In the southwest US (Arizona/Utah) it’s not uncommon to come across a single mantle / very short T4 bit in what is otherwise a mostly T1-T2 trail with occasional T3 moments.
There’s a lot of stairs in the Sierra Nevada from the pack mule era like I described here. There were also some stairs in Canada in photos I outlined in the smoothness/surface thread.
One other twist is that an otherwise easily walkable trail can have a water bar which is more than 24cm high which makes it smoothness=impassible. Hazard seems most appropriate for something which very briefly increases the difficulty/technique.
Similarly, GaiaGPS by default hides any route with T5-T6 (you have to opt into a “mountaineering layer”). I think Caltopo stipples them differently and you can pull up metadata in a side drawer.
Whether or not they appear in normal maps is up to the map renderer @ IanH.