If you force touch the UI, it does say "Not Connected" when you hit the button, not "Disabled."
I can understand the confusion, because they have re-used an old UI element for a new purpose, but there's no reason the button should mean "Disable Radio" rather than "Disconnect." And as cptide mentions, the button now has three states: blue for connected, grey for disconnected, grey with a line through for disabled. Once you know this, I think it makes a lot of sense.
If you want the old behavior, it's still there in settings, where the on-off toggle will turn off the radio itself.
Personally, I much prefer the new system (I far more often just want to disconnect from the current network/devices than disable it entirely), and think the new control center is much improved over the old one.