I suppose this is as good a place as any to mention that many community members would like the option to change the dim level without actually turning the device on.
This is commonly used when you want the device to be ready for the next time someone manually presses the switch, but you don’t actually want the light on yet. Or you want it to be ready for the next time a motion sensor triggers it.
For example, there might be a use case that from 7 AM in the morning until 11 at night, the light comes on at 100% when the switch is pressed. But from 11 PM until 6:59 AM you want the light to come on at 60%.
So you have a routine that changes the dim level every night at 11 PM. But that doesn’t mean you want the light to come on then. You just want it to be ready to come on if needed, but not at full brightness during that time period.
This does mean that you are separating the “on” setting, and the “level” setting, but that’s what the third-party standards do for Z wave and Zigbee.
I have seen on some other Z wave platforms a convention that setting to 100% means “set and turn on” while setting to 99% down to 1% just changes the level and requires a separate on command to turn the light on. (Setting to 0% also turns the light off.)
I suppose it’s possible that if they’ve hired some engineers who had previously worked on one of those other platforms, they might have brought that convention with them. 
By the way, you see the same conventions in some dumb dimmer switches. The ones with a rotary dial. For some of these, turning the dial changes the setting, but doesn’t turn the light on or off – – you have to press the button in the middle to do that. For others, any change on the dial, turns the light on to that setting. And there are even a few, particularly the ones designed for “mid century modern” homes from the 1960s, where turning the dial does not normally turn the light on until you press the button, but if you turn it all the way as far as it will go, the light does come on to maximum brightness.
So there are different ways to handle this, but I agree, it would be nice if the explanation to the end-user was clearer. And for an automated system, I do think it makes sense to provide the option to only set the level. From a UI standpoint maybe this should be a checkbox for “turn on” with a default of checked. That way doing the minimum work in setting up a routine would cause the light to come on at that level, but you could uncheck the box if you only wanted to change the level in order to make the light ready for the next time it came on. A “baby sleeping” option. 
FWIW
