Not that I'm much invested in this, but what would you want to see there when a track contains vocals, but no actual words?
(vocalizing, scat, yodeling, etc.)
I don't think you can call that 'instrumental'?
Forgot to comment on this earlier
Like any system of categorisation, there is always those borderline ones.
Like Hocus Pocus by 70's prog rock group Focus. It's yodelling and operatic vocalisations but it's classed as an Instrumental.
Same as the disco hit Fly, Robin, Fly by Silver Convention. Despite having recognisable lyrics, it's still listed as an Instrumental.
Maybe it's because the lyrics only contain 6 words sung repeatedly!