Why do some 'performed' callbacks seem to be called twice (or zero times) per frame?

Hello,
As per title my question is why, in the particular case of a Pass Through / Vector2 value (given by Pointer or Mouse bindings), does the performed callback seem to be called twice per frame?
I put together a simple test case.
In the zip file you'll find

1. MainControls.inputactions
2. MainControls.cs
3. InputTestCase.cs

Import in your asset and attach InputTestCase to anything.
The key code lines are the following:

Code (CSharp):

1.  
2. controls.Gameplay.Aim.performed += (x) => { aimPerformedCount++; };
3.  

increment aimPerformedCount every time it's called

Code (CSharp):

1.  
2. Debug.LogFormat("Aim: {0} ; Fire1: {1} ; Fire2: {2}", aimPerformedCount, firePrimPerformedCount, fireSecPerformedCount);
3. aimPerformedCount = 0;
4.  

at the end of the Update, print out the counter and and set it to 0

The output is always either 0 or 2. So my question can be reduced to why is it not 1?

I'm testing this in Unity 2019.4.6 with Input System 1.0.2. I know it's not up to date but I have faith in those LTS letters attached to the version. And it'd be good to know if it behaves similarly with later versions, if anyone is up for testing.

 

Answering my own question: the sole, simple reason is that I have 2 bindings configured for the Aim action. Pointer counts as Mouse I think. After removing the Pointer binding the output is either 0 or 1.