Setting Fade/Transition Rate at on/off for Lightify?

Hi everyone, I’ve got a large number of Osram Lightify bulbs/FLEX lights that are mostly on the latest Smartthings provided firmware (492) and are using the standard ZLL RGBW DTH (to allow local processing). Two devices that are on identical firmware are acting differently when turning on/off.

One is fading on/off (as Hue bulbs do), the other is not fading at all. I suspect this is from where I set it to fade through the Osram gateway and app before transferring it over to Smartthings. It seems that it is retaining the transition time ‘in device’.

I have tried using a custom DTH and setting the transition (which works on both devices), but as soon as I revert to ZLL (to allow local processing) it reverts to normal.

So… the question is, can I ‘read’ the setting for this on the device that is fading, and can I ‘write’ this same attribute to all of my other Osram bulbs in ST?

I have researched this, and found mention of the following ZigBee attribute that can set it:

zigbee.writeAttribute(0x0008, 0x10, 0x21, 0x000A)

…though I dont know if 1) this is correct, and 2) if/how you can read and write these attributes to devices in ST?

Thanks in advance for any help!!