Somewhere, this has been discussed before (I'll have a look). I can't remember but I think my own conclusion was that at least some of them are in that category you mentioned yesterday - they've got a folkloric explanation that's not really recognised as folklore, because it doesn't involve dragons or saints. There's marks on the rocks but they're older than metal arrow marks.

Or maybe not.

Anyway there's a lot of them about and when you look them up on Coflein it gets very confusing because it's not clear what they are and they are ALL called 'Arrow Stone'.