Tony,
it's just a assumption but I think it's working this way to give the administrator of the WLAN controller more options to configure it.
I unterstand that in your case your customer want to have it enabled on all APs for every SSID (global enable) but on the other hand a lot more customers want to have it only on certain APs & SSIDs so a global enable of the function would be not working for this scenario,
But that's just my interpretation of the configiration option.
So let's wait for a Extreme employee to give some input - it's 9am already so after the first coffee I'm pretty sure that someone will respond to the post 🙂
-Ron