Before a Warrant Officer jumps into print, Warrant Officers as such are in no way NCOs in the British service of course.
From memory [I can provide collateral if needs be] there was a hoohah on the subject c. 1885 when a minor functionary made that mistake in print. It was sharply and officially corrected. Subsequent Queens and Kings have maintained that line in Regulations for the Army.
A partial cause of slight blurring might be that both WOs and SNCOs inhabit the same mess.