What obvious other factor would you have to consider before making this change and allowing the increased load it implies? You're concerned about the slip resistance of a slip-critical joint you're designing.
You had hoped to avoid the expense of specifying a slip-resistant coating for the joint members, but now decide that you must do so.
You specify zinc spray over a grit-blasted joint surface instead of using the joint in the as-received condition. By what percentage do you expect this will increase the shear load that this joint can support?