M1 Macbook export photos not using performance cores

My device is Macbook Air M1/ 8core CPU/8core GPU/16G RAM

Lrc is 11.4.

When I'm exporting photos, all 4 performance cores are nearly zero usage.

Meanwhile all 4 efficiency cores are 100% occupied.

And it doesn't matter whether I choose "GPU for exporting" or not. Both the same.

Why it's like that?