Some games hog the mouse input when two apps are open simultaneously

[Managor]

Demonstrative video: https://youtu.be/dPuvd1Pbiq4
Some games hog the mouse input from other apps that are open alongside them in gamemode. It doesn't seem to make a difference if the other app is Steam or non-Steam. There doesn't seem to be any outward commonality with the games I've tested and only very few games have this behavior.

The games I've identified are:
Digimon World: Next Order
Outer Wilds
Bioshock Remastered
Cave Story+
Deus Ex: Game of the Year Edition
Insaniquarium
Mafia

Reproduction steps:
1. Open one of the listed games
2. Launch something like discord as a second program
3. Open the second program
4. Attempt to click on anything on the second program

Expected results:
The second program should get mouse input

What actually happens
The second program doesn't get any mouse input from the pointer or buttons

[Managor]

Further comment: If I simultaneously open two games that hog the mouse, like Digimon World: Next Order and Outer Wilds, both of them receive the input

[Managor]

I have been informed that this can also be reproduced with Fallout New Vegas+Nexus Mod Manager and Persona 5+FlawlessWidescreen. I am unable to test myself.