If I was shooting mostly coated (or plain) lead I would be doing it in two steps same as you.
In my experience - With quality jacketed bullets, brass that is fairly consistent in length, AND if you are going for minimal on the belling and crimping... Shaving and crushing only happen when the dies are not adjusted properly.
The more a guy tries to work (crimp) the case mouth beyond just ironing out the belling that was done - The more difficult it will be to get everything running smoothly in a single step with a single die. Your comments about the brass length / mixed headstamps and the amount of crimp applied were all spot on but become even MORE important as that die body gets turned down for more crimp than the bare minimum needed to iron out the belling that the other die did.
I like my RCBS 9mm dies. They make a special seater plug for the Speer Gold Dot 9mm bullets which cost nothing but an email. Same seater plug works like a champ with many other brands of 9mm HP I tend to use as well but not telling RCBS that...
I like the way they did the belling stems you get with many of their straight wall pistol dies. The tiny step before the major belling works well for me with the projectiles I like to use normally.
With my dies this was the difference in size between the steps (and my craptastic sketch of the shape due to not having a macro camera here right now):
The brass smears give a good tell of how that expander was adjusted and what it was doing to the brass it was used with in that session.
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