css selection pseudo-element animation

Question

Why doesn't the animation property works on ::selection selector in CSS?

Basic Test Case:

@keyframes frames{ 
  50%{ color:red } 
}
@-webkit-keyframes frames{ 
  50%{ color:red } 
}

::selection        { background:#EEE;         animation:0.4s frames infinite; }
::-moz-selection   { background:#EEE;         animation:0.4s frames infinite; }
::-webkit-selection{ background:#EEE; -webkit-animation:0.4s frames infinite; }

<h2>Selected text should be animated:</h2>
CSS3 animations make it possible to animate transitions from one CSS style configuration to another. Animations consist of two components, a style describing the CSS animation and a set of keyframes that indicate the start and end states of the animation's style, as well as possible intermediate waypoints along the way.

Answer 1

I wrote Tab Atkins and he answers:

In general, most browsers have trouble running animations on pseudo-elements. We're gradually fixing these issues, but it's slow work, because pseudo-elements are pretty complicated to handle in the browser.

On top of that, the ::selection pseudo-element is the most complicated pseudo-element in all of CSS. It's so complicated, we explicitly undefined it in our specs until we figure out how to actually specify it in a way that works well.

Answer 2

Most of what I see on animation is:

Applies To: all elements, ::before and ::after pseudo-elements

Which suggests not other pseudo-elements or states?