It seems to me that the extractor shoulder has no effect at all with a cartridge in place.
I tend to agree with Ken here, and what hes saying makes sense.
If you use the face of the loaded chamber indicator as a reference, when there is no round present, the indicator is flush with the slide. Put a clean factory round in the gun, and the indicator now sits 0.031" higher than the slide. That leads me to believe that with a round in the gun, the shoulder is also going to be the same distance off its "rest" in the slide, and never will bottom out.
For me, the jurys still out, as Im right back where I was, with reloads having the issue, and factory rounds functioning fine, even with what I think is a worn extractor.