[BUG] GPU usage even with audio+video disabled

[Linerd4]

I managed to disable audio and video output on Chiaki, but I'd expect GPU (and partially CPU too) usage to go around 3/5% since it should have nothing to render nor decode, but this is the result I got from my main PC and a spare laptop I got around:

PC (intel I7-7700 with Intel HD Graphics 630):

Laptop (AMD A6-9225 RADEON R4, 5 COMPUTE CORES 2C+3G) undervolted:

Same laptop not undervolted:

Have I missed some option to tweak? I tried everything but nothing seems to make it go down...