I don't have a current iPod nano. I'm saying sandisk figured out that the accelerometer shouldn't be active by default all the time. Why hasn't Apple Caught on?
The nano does have a menu setting to turn off shake-to-shuffle. It's not mandatory.
The accelerometer is a mechanical device that produces an output signal - what the firmware does with that signal is entirely up to the programming. It would be a fairly easy programming fix to give the option to turn off cover-flow and stay in menu mode regardless the orientation of the nano. Whether or not the accelerometer itself can be "turned off" so it doesn't pull any juice would be a function of the hardware architecture.
So yeah, a fix is absolutely possible.