Well... it does. I'm sure they are slightly out of round, but we are talking less than .001" here, unless the mold was worse than that to begin with. I've done it on a few molds. They grow concentrically, and I have not had any finning.
Lapping out a mold on the other hand is not easy. I tried on a nice old NEI mold. I took my time, thought I did a good job. I now have a "mold" that casts bullets .007" out of round, and even with sizing the low spot still isn't as big as I need it to be. That mold is *****. I sure wish I had just left the aluminum tape in there. Lapping is an art best left for a talented hand, not a beginner.