Doesn't most DJing software support constant-pitch speed adjustment?

Pitch and speed are inherently linked when you are dealing with physical vinyl, but time-stretching in software isn't too complicated.

A little niche, but that would be handy while directing an a capella choir. Giving starting pitches without a pitch pipe or tuning fork would be useful.

If you compose, i can see it being a nice speed up on your process

people with perfect pitch can recognize when pitch has been shifted, but it's not like they perceive it (necessarily) as wrong or annoying - it's a matter of taste. most of them can still enjoy microtones, detuned tracks, and beatmatched dj mixes just like everybody else.