I see it there, from T5 (verbatim) on, mountaineering boots required. In Swiss Alpine Club® scale from 2023, T5 can include UIAA II for short stretches, in OSM sac scale UIAA II only in T6 (verbatim), a.k.a. difficult_alpine_hiking.
It will be a long way to unbind OSM sac_scale from its origins.
PS: I did the UIAA III with ease in Oxford shoes and I am not a climber, I maxed out at French 5a top rope once I tried.