Very good point Ben.
It's always good to know the FUNCTION of every part, groove, cut, notch in the SKS.
I tried to get a easier to see picture of the proper installation but it's dark in there

You can see the crossbar that runs across the top of the trigger bar and the clearance notch cut in the disconnector for that crossbar.
Note that some early (years?) Russian Trigger groups do not have this added feature.

In this second picture you can see that the hammer kicks the Rebound Disconnector when the action cycles and cocks the hammer forcing the trigger bar off the sear.

I suggest owners examine how the hammer/disconnector/rebound disconnector/trigger bar interact.
I would post a video but it takes more than two hands

Just watch through the inspection hole as you slowly cock the hammer.