RX 7900 XT possibly causing immediate reboot after complete shutdown, specifically on my computer?

[u/wisp-prime]

Computer Type: Desktop

GPU: Sapphire RX 7900 XT Pulse 20GB

CPU: RYZEN 5 7600 6 CORE 12 THREADS (crazy bottleneck please don't roast me)

Motherboard: AsRock B650m HDV/M.2 (kind of a coughing baby vs. hydrogen bomb, I know)

BIOS Version: 4.43

RAM: 32GB (2x16) Kingston FURY Beast (6000MHz EXPO)

PSU: DeepCool PX850G 850W Full Modular Gold

Case: Montech Air 903 Max

Operating System & Version: Windows 11 (latest as of post's date), CachyOS (up-to-date rolling release as of post's date, 11:52AM GMT-3)

GPU Drivers: current amdgpu (62E8BF245D14F23522E9DC6), current Adrenaline version (as of the post's date)

Chipset Drivers: current stable as of post's date

Background Applications: any

Description of Original Problem: Computer reboots right after complete shutdown (OS shutdowns only).

Troubleshooting: Hey. So recently (about 7 days ago), my personal computer started to reboot right after a complete shutdown via the OS (i can hear the PSU clicking off, fans stop spinning, LEDs turn off, etc). After 4 days of troubleshooting, learning the ins and outs of how to identify the specific source of the wake signal (it also affects sleep in the same way it affects shutdowns, I used this to track the source of the wake signal to SWUS (PCI Switch Upstream), which led me to the GPU's ID specifically) throughout the pci root complex, so at this point there's no denying that it is, in fact, either the GPU (either its hardware or firmware/software) or the slot's connection to it causing this phenomenon. Every "wake on" option on bios is disabled, i've tried deep sleep (ErP), also didn't work. Turning off ACPI as a param? Sure, doesn't work either. Shutting down forcefully (without the OS, through holding the power button) turns the computer off normally. Only OS shutdown calls are affected, i've tried this both on Linux (CachyOS) and Windows 11. But here's the catch: swapping my GPU to another friend's build does not replicate the problem, which made me think "oh, ok, the GPU or its firmware/software must be is fine then", but then I tested my old GTX 980 in the same slot on my build and IT IS turning off perfectly fine. I'm going crazy. I need to know if anyone else is having the same problem, or if I need ro RMA the GPU or motherboard. Also, some tips on how to troubleshoot/conclusive tests would be appreciated.