What do you mean by this? The back button is involved in system UI and apps should be limited in their ability to steal it, but fast forward is an action that makes no sense outside the context of an app
Either that or can't skip ads, ala legal dvd playback
There's no platform with a standardized "fast forward" experience - Apple TV, Google TV, Fire Sticks, whatever are apps running on a device and those apps all implement their own navigation controls.
To be completely cynical about it, if APV hadn't demanded the os support, I think some other party probably would have.
So when they just stop your show to try to sell insurance or whatever, and you try to ffwd through that noise, you get a little caption that informs you that "fast forward is not available during ads".