Maybe interesting for one reading this. I was annoyed by the – on the other hand – impressing Ticwatch Pro 3 GPS, as it always switches on backlight when you turn your wrist. This is great when awaken, but at night wakes me up. Even the DND modus does not help. But here you are, I think this will help you. Till the Firmware is getting updated, we might can live with the following workaround:
Select the Cinema / Kinomodus. The second icon in the lower row. The Watch does not light up anymore. If you want to disable it, press the power button.
Hope this helps. :-) Interested in a watch? Use this link!