Yes, Gigabyte also has this feature available in the Windows RGB Fusion App and the Bios. However, why that's happening is the least of my issues, this has happed in the past too when i've had the PC shut down due to a bad extension cable. The PC would should down and the RGB would stay on.Glad that you got something to test and that the gpu seems at fault here per your tests and observations.
Was it a recent bios update or something which is resulting in Ram leds to turn on without even powering on the system?
In your case I highly suspect that after a bios reset or auto-bios reset due to the failure, the stock factory settings might have kicked in resulting in the ram leds to turn on idling. Google for more or better ask this specific behavior on reddit or someone here who owns Aorus with keen interest in rgb stuff (like me)
This behavior is common in fact normal on Asus rog mobos. I own one and the moment I just turn on the mains the mobo leds/ logo etc. all light up though in bios there's an option to toggle such feature (3-4 options to chose from)
So if thats the case then your mobo seems perfectly fine here. But again its under warranty so you can get it rmaed if somethings wrong.
You got the multimeter so you can google for certain mobo chip level bus tests which might give you better insights as to whats kicking in ram leds. But I would highly press you to dig inside bios as my 7th sense says some setting might be toggling them on..
I found an identical issue on Reddit, have replied there but have not heard back from the OP.
Your above reddit screens are not RGB but actually Ram debug LEDs which is not related to me as when my GPU is installed i do not get ANY debug LEDS.
I have been looking at at YT and it seems shorts on the 1080Ti appear to be common, this prevents PC startup, so as much i was hoping it was not the GPU, I believe it is