GPU PPT should be reported as averaged over the past second, not instantaneous
Running Linux 6.6.2, AMD Ryzen 7 PRO 7840HS:
amdgpu-pci-c300
Adapter: PCI adapter
vddgfx: 1.44 V
vddnb: 660.00 mV
edge: +34.0°C
PPT: 16.12 W (avg = 6.14 W)
PPT fluctuates between 4 and 17W despite the system being completely idle (just Xorg and xterm are open, compositing is not enabled) and the APU temperature being around 36C.
turbostat --quiet --num_iterations 1 --interval 1 --show PkgWatt --Summary
Reports under 1W.
Under Windows with HWiNFO64 and AMD drivers own monitoring the situation is no different. AMD Windows drivers report additional power being consumed well above what the total package power consumption (which includes the iGPU power consumption AFAIK) is.
I don't know what GPU registers you are polling but they don't seem to report the correct data for iGPUs.