I just tried something. In PP all the fields you can change in the effects tab are highlighted blue. All you need to do it mouse over it and drag to change its value. I also tried this in FCP X. Yes, you can just mouse over the number you want to change and change it. You will get little pointers that indicate you can scroll the value up and down. The numbers do change to blue in some cases. If you want to add a certain number you can select it and the blue box will indicate you can enter a number. This is pretty much the same as it works in PP.
Also, the reason the 0 field for the X and Y value are off to the right is because it leaves room for a value of 4 digits or more.
Pretty logical to me.