There’s more linkage between AT and the TR plans than that. What you are describing is Trainnow.
The way that AT works today, there is some way it knows the intent (this workout should be productive, this one should be Achievable, etc.) of the workouts in the TR plans. And it uses this, plus what it “sees” in your performance to then change the intent of the workout. So right now, AT is tightly coupled to TR workouts. So if Zwift wanted AT, they need TR plans, which means TR calendar.