I definitely like this approach with un-turned brass. I do however wonder if the result would be equal, or if it would be inferior, if you simply used an expander ball .002" under bullet diameter in the Forster sizer. If the same result coul be obtaine with one step less, then it only makes sense. I turn necks on match guns, so the only thing I run over an expander is hunting guns, but I've not identified any noticeable accuracy issues from condensing the steps. I can't determine that with my match guns because my necks are turned.
Using a Whidden FLS die with 0.334 bushing and 0.306 expander produced <0.0015 run out on my turned (to ~ 0.014) Lapua case necks. The expander ball lightly touches the inside of the case neck as the ram is lowered. For comparison, I then full length sized a few cases in the same die but without the expander ball and then opened up the necks used my K&M 0.307 expander - this produced ~0.004 run out and is consistent with past experiences.
Body sizing and then using a Lee Collet die gives me a result similar to the Whidden die.
Martin