The code for both those action methods could be put into a class in the Models folder, and the controller action methods could call the methods in the Models' class in an async manner as needed, or one method in the Models' class can call the other method in the Models' class in an async manner, as examples.
It's about seperation of concerns.
In computer science, separation of concerns (SoC) is a design principle for separating a computer program into distinct sections such that each section addresses a separate concern. A concern is a set of information that affects the code of a computer program.
So don't get SoC twisted, becuase the wiki link talks about layers that is another form of using SoC.
It's about getting the code out of controller action methods, keeping the controller thin and have controller action methods call methods on classes/objects in the Models folder by using SoC principles.