Lolol. Nice wriggle. :-))

Unit names with prefixes are treated "as per 9.2" because that's the clause that deals with unit names, while "A derived unit is usually singular" is stated explicitly and derived units would not, therefore, be "as per 9.2".

Science-based I am but my interest here is mainly in English. The NIST stuff was all news to me and just a chance for a bit of pedantic quibbling, er, I mean fun, lol. ;-)

The last word's yours, my friend (unless you drop a big clanger, lolol).