PointerExit being called by "Positive/Negative Button" input?

Using the new GUI system, I'm using PointerEnter to display a tooltip when the user hovers the mouse over an inventory item. This works fine until I press one of my buttons to move the character (ASDW), and the tooltip disappears. After a lot of inspection, I figured out that pressing the "Negative Button" and "Positive Button" input commands are causing PointerExit to fire.

I don't want to jump the gun, but this seems like a potential bug to me-- I haven't been able to find an explanation...

PointerExit being called by "Positive/Negative Button" input?