iOS Mobile - Mouse Input vs Touch Input

So I just discovered
(also from the insistence of my senior programmer for using mouse input on the iPad)
that OnMouseDown works on iOS mobile devices, without the need for any touch input scripting.

But according to Unity’s official documentation

OnMouseDown (and all the other methods of mouse input) is not supported on Unity iOS at all.
All this while I was deceived into not using it at all for my touchscreen apps. But using mouse inputs makes it A LOT easier for me to run tests and debugging on the Unity editor.

So what’s up?

Are there problems that I will eventually encounter in the long run if I were to use OnMouseEvents for touchscreen devices?

It also works for android. You see touch controls are basically handling the tap as a click.
But that way you can’t have multi-touch controls, if you need the user to touch more than one thing at once (pinch to zoom, or a virtual joystick control scheme) then you won’t be able to.