Yeah, I read the BMC article about it: damp & lots of loose rock as well as smoothed holds, so accept alpine_hiking. See https://www.thebmc.co.uk/how-to-scramble-jacks-rake

I think in practice UK Scramble Scale 1 actually overlaps SAC T3 & T4 & so on up the scales. Might be worth adding https://taginfo.openstreetmap.org/keys/scramble, but it's scarcely used & undocumented. But thanks to various people, specifically Alex who's done a few places in the Highlands too, SAC Scale usage in UK seems to be rather more consistent than it was.