Something like input switching should operate below the OS.
Input switching on my TV doesn't even cross the Doherty threshold, or at least not in any way that I notice. And believe me, I get as irritated as anyone with laggy TV menus - which is one reason I refuse to buy Samsung at this point.
But not all. So, clearly it doesn't have to be below the OS level. I agree it needs to be quick, responsive and reliable, but that doesn't preclude it from being implemented in the OS.