A kite is grunty when you can hear its grunt.
Only low end grunt is important, because you can actually hear the kite's grunt only when the apparent wind is really light.
The apparent wind is light only when the rider is static or moving very slowly. That's why low end grunt is a synonim of light wind static pull.
But don't be mistaken: static refers to the rider, not the kite. In the fun sizes, most of the grunt will come from the kite's movement.
What makes a grunty kite?
A combination of a deep profile and low aspect ratio.
Race kites are not grunty kites. They are high L/D, and thus shallow profile and high aspect kites.
They pull at higher apparent wind speeds, and do not move much.
You cannot hear their grunt.
Yeh I'm more in this guys camp when it comes to grunt, well explained.