Context: I installed an app called "Scroll Reverser" which will allow me to use the natural scrolling setting for my trackpad and the opposite scrolling setting for my mouse scroll wheel. The application requires the Privacy permission "Input Monitoring". The description of this is to "Allow the apps to monitor input from your keyboard even while using other apps".
So does Apple just consider mouse inputs, like scrolling, an "input from your keyboard"?
The app was recommended by another user on this site: How to separate "mouse" and "trackpad" settings?
Best Answer
Scrolling can be a keyboard input. For example, using the arrow keys on a keyboard will often scroll the window.
While I have no experience with the Scroll Reverser app, a quick check shows the source code is available. And, according to its Read Me file:
Since the app uses Quartz Event Services then it's basically monitoring low level inputs from users. More technical information is available on the Quartz Event Services page on Apple's Developer site.
But essentially, monitoring low level inputs also means monitoring keyboard inputs.