I think you're misinterpreting it. Characters beyond the caret ^ are attributes of the word/expression for
zo_strformat, so that it uses the proper form. Thus "sanded beech^ns" is not "sanded beech^n"s, it's "sanded beech" with attributes 'n' (neuter gender) and 's' (not described in that post, maybe it means "don't append s for plural").
Lua Code:
zo_strformat("<<2[1/$d]>> <<tm:1>>", "sanded beech^ns", 5)
-- 5 Sanded Beech