A scene controller is pretty much defined within the zwave spec. So smartthings can capture the button press information from those because the assumption is that you are switching between scenes and only one will be active at one time. So you have a morning scene, and evening scene, and a movie scene. But they are mutually exclusive. If you press the evening scene, you get that scene, the morning scene is no longer active even if thatās a completely different set of devices.
As Leviton designed their zone controllers, they were initially intended for a large room that would have different areas of lighting. So in a kitchen, you might have lighting over The sink, lighting under the counters, the overhead light fixture, and lighting over the stove. You might first turn on the overhead light, and then decide that you also wanted to turn on the under counter lighting. So you could have multiple zones active at the same time. Leviton describes these as different light sources and expects them to be different physical devices.

with the zone controllers it was not supposed to turn off the other zones just because another one was turned on. They are not mutually exclusive.
Hereās Levitonās own explanation:
Zone Control is your key to controlling multiple light sources in many rooms or areas of your home with one push of a button on a zone controller. Scene Control lets you vary the light levels in a room for any activity or change the ambiance with one touch on a scene controller.
So with the zone controller, each button is meant to control a different physical set of lights, and each button is independent of the others. They could all four be āonā at the same time as Leviton designed them.
With the scene controller, which again is pretty close to the Z wave specification, each button is a different scene but might apply to the same physical lights. And they are mutually exclusive: turning on button two would then override whatever was associated with buttons one, three, and four.
Leviton āzonesā. Each is expected to be a different set of physical devices.ā

Look closely: these are rocker buttons, with the left side being on and the right side being off.
Leviton āScenes.ā This closely matches the zwave specification. This could all be the same physical devices, but at different dim levels. Or somewhat different combinations of devices.

These are momentary buttons which just select that scene, except for the bottom button.
You can see the difference in the physical action of these in the following video, which is a Leviton-produced marketing piece.
Right around 2:00 , you can see a zone controller with the horizontal toggle switches. Left for on, right for off, and each button is independent of the others.
Then around 3:10, you can see a scene controller with the four momentary buttons. Turning on one button turns off the others.