I believe I read somewhere that the Zigbee protocol doesn’t allow brightness changes while off. If that’s true, then no lights (that properly implement the protocol) would be able to do this.
I don’t see a reason why Inovelli couldn’t add a special command to achieve the same thing, though. This would be easier if the firmware were open source. It seems like a reasonable request, but I’d imagine other higher priority items will always be prioritized.
In the meantime, using parameter 13 seems to be working for me. (See above.) I’m still worried about too many writes, but I’m going to try to dig in and see if my code is actually sending messages to the device when the brightness value doesn’t change. (Wrapping it in a conditional is a simple enough change.) I don’t know the code to set the parameter for z2m, but I doubt it would be hard to find it and adapt what I did.