Heya - just a small gap in my knowledge

Hello Forum! I haven't been here for a while!

Anyway theirs a question I have, Fast Moving units, some units have this stat but I cannot seem to add it as an attribute (I'm trying to give it to a Celtic Warrior unit I've added)

Help Appreciated.
Thanks

Its based on the skeleton of the model the unit is using.

Seems like an odd system of doing it.
But it defiantly seems to be correct.
Thanks bro