Stalwart Speed won't stack quickness

This trait says "when you grant aegis or stability, grant quickness."

I run both shouts "retreat" and "stand your ground". Casting one after another does not stack the quickness Only the first skill used grants quickness. I can use either first, doesn't stack if used in quick succession. There seems to be a hidden cooldown on quickness because if I use stability first I will not get the quickness from aegis until stability wears off, and f I use aegis first quickness will not stack with stability unless I wait some. The boons from "retreat" are active still and I am able to gain quickness just not rapidly enough for them to stack.

Why?

Someone help me understand whats going on here.

The trait has a cooldown of 5 seconds.

Well this don't seem right at all. Quickness itself stacks in duration and nothing in game says anything about this trait having a cooldown. Wiki likewise does not make this distinction. This would appear to be the only exception to stacking and is just crude. Should be brought in line with the correct way of stacking duration.