It is not written anywhere but mobiles don’t have the power as PC
I disagree. If you look at cpu alone you will find mobile cpus surprisingly high in the list.
https://www.cpubenchmark.net/cross-platform.html
But graphics are mostly done in the gpu and the gpu of a mobile is optimised as well.
What I am trying to say is this: games on pc will have settings to make them run on low end desktops. If they create the game so only 1% of the desktop pcs can run it, they miss out on potential customers. Also there are laptops.
Combine that with the lower resolution of a mobile screen and a slower frame rate and you will have mobile games seemingly outperform their desktop version. Seemingly. Going down from 4k resolution to 1/8 to 1/16 of the resolution and cutting frame rate by /2 or /4 and suddenly you only need 1/20th of the computing power. And this is not even considering reducing the bells and whistles of the graphics. Only bare bone pixels per second.
tl;dr Games will be optimised for the platform they run on.