When you use any kind of specialty switch, like (obviously not relevant here) a motion sensor, timer, etc. a neutral is best. There are motion sensors that pull a bit of current through the circuit itself, but they are terrible at best and often don't work with LED lighting, which is also code now.

I suspect the code mentioned is meant to prevent shoddy sparkies from lazily grabbing neutrals from nearby circuits, which can result in shared neutrals (ask me how I know this).

I can't honestly think of a reason why you'd use anything other than a dumb toggle switch for an under-sink cutoff for a DW/Disposal, but it's probably easier and safer to just say "all switch locations need a neutral" than to specify "except under kitchen cabinets where the switch is only used for an appliance cutoff".