I answered my own question by doing more internet research. I found this on the Cast Boolits website:
"Well the problem with the marks on the primer is the fact that the ejector is machined into the bolt face almost half way across the case head. The ejector is supported by a spring which needless to say is far more flexible than a solid piece of steel. When firing the pressure exerted on the primer overcomes the force of the ejector and causes it to extrude back into the ejector, which for these purposes is unsupported. Simply put, the ejector spring compresses and allows the primer to flow back slightly.
All that sound really bad, but in actuality it's really only a problem if your concerned about the look of your fired brass."
end of concern.
