For example for `DragZoom`: Let's say `Shift`is pressed and a `mousedown` occurs, this activates the interaction. Now, a `touchstart` occurs (which is not handled by `handlePointerDown`). But the following `pointermove` and `pointerup` events issued from this touch, would be handled by the interaction (without the check). So, the interaction might get deactivated before the `mouseup` happens.
Anyway, it doesn't work that you can zoom with the `DragZoom` while touching the screen. But with these checks I try to avoid that the interactions are left in a broken state.