Why would anyone need a phase switch on an instrument track? On audio tracks, you may have a DI'd guitar on one track and the same guitar mic'd on another. If they are out of phase, you need to flip it on one track.
Or, you may have a top snare mic and a bottom snare mic, requiring you to flip the bottom mic.
But why on earth would you need to flip the phase on a simple instrument track? Seems like a
very rare scenario to me.