Thanks @chocolacode for helping.
Indeed, the “Input Button” event has a name parameter which is directly related to Unity’s “Project Settings -> Input”. This way, you can basically map a name to a keyboard, mouse or gamepad input.
For example, Unity by default comes with a named input “Fire 1”. This by default maps to Control key, Left mouse button as well as gamepad button 0. This is just how Unity works.
On the other hand, if you want to simply specify the exact keyboard key that the event node is using, then it would be much better to just use the “Input Keyboard” event node.