For what i saw, it only uses a Data Table with the ThrowGrenade row, not the brush key set.
I have found a brush key set entry in /All/Game/UI/Foundation/Platform/Input/KeyboardMouse/CommonInput_KeyboardMouse, but i cannot find it used anywhere
It is using the data table row, which is assigned to a single key (Q in this case) and in the Common Input Base Controller Data, there is not a Input Brush Key Set for the grenade, so it uses the Input Brush Data Map for the Q button