Shadow / dark spot on screen of new iPad Pro (12.9 inch, 5th gen)

When using my iPad Pro 12.9inch, 5th gen to play a games (Genshin Impact), I start to notice a shadow halo (for lack of a better term) to appear on my screen after a few minutes of playing.

This is especially visible when I leave the game and open a blank document (as visible in the photos with a blank layer in procreate).

This halo originates especially on the spot of the screen where the iPad begins to heat up when playing the game.

The photographs don't do it justice, and after some time it becomes quite irritating to look at.

Is this a defect of the screen? Or are other people experiencing this or know where it comes from?

Photos of the shadow halo on my screen:

(just for clarification, the white dots in the second photo on the iPad screen are just a reflection of lights in the background.)