The mandrel does care.
New brass is easier to fit to a particular turning mandrel(through expansion) because it was fully formed in manufacture, pretty much ready to load. This is the basis for expander mandrel size.
With fired cases all dimensions change, and you're relying on die downsizing, springback, expansion, and springback again, to leave whatever mandrel fit you end up with.
It can be done, some(with wildcats) may have no choice if turning. Some take the inside neck reaming path instead of outside neck turning.
But ideally, you would turn before firing. And most have to(in a tight neck chamber) because the loaded necks wouldn't fit until turned.
Trial & error for you.