[vetinari]

To quote the Intel docs:

> Plane scaling is [sic] supports both linear and non-linear scaling modes. The scaling mode is programmed in the PS_CTRL. In HDR mode, scaling and blending operations are generally performed in linear mode.

To be limited to sRGB would mean, that the hardware is pretty much limited to SDR. That would make it unusable in mainstream market today; just good enough for low-end SBCs.