I wouldn't dare try defining the term if it were a serious discussion... it's obviously subjective depending on everyone's own opinions. .. For instance, I can make some complex spreadsheets, but I wouldn't call that programming excepts in the most basic sense at best. Still, I suspect if someone is creating a "toast message" to pop up information... I'd assume they are creating some type of app or program.
I could certainly venture a guess ( ie big grain of salt ) on why a toast message from an app/program that is in the background is no longer supported... would be to help save power. It seems that the newer Android OS versions allow fewer background apps running in the background without specific permissions for that purpose... it's make sense if they are doing similar things for toasts and notifications as well. Still, that is coming from a non-dev type and may have nothing to do with it.
Of course it seems at times that Google acquires, creates and then kills perfectly good stuff quite often .. often without saying why they did it. So at that point, it's probably anyone's guess.