Actually, the intended purpose of a trigger stop is to limit the amount of trigger travel after the sear breaks so the trigger doesn't build up inertia before encountering the limit of its travel and possibly affect the gun's point of aim. This is a target-shooting feature more that a combat one, which might be why 6" guns seem to have it most often.

Having said that, I have a 4" 66-2 that has a stop. I posted a photo of it once and someone on here messaged me about its rarity on that barrel length.

Ed