Spacing is far more abstractable than hard values of "margin" and "padding".
There are numerous CSS properties that permit 2, 3, and 4-value syntaxes for positioning styles. But, 3-value syntaxes never took off -> so 2 and 4 value syntaxes for shorthand vertical / horizontal and all 4 cardinal directions + universal application in 1 value syntax.
In other words. It's the exact same thing. So, let us rename it as such.
If you're attentive... You realize this means you also need negative values. Clearly, negative padding doesn't make much sense. But, it does for all other properties that take positioning adjustments.
