Just throwing this out there, as I am more of a tinkerer than any kind of expert, but I think that one of the issues with the WSSM brass is that it is thick in the case neck. My 223wssm brass is 0.021" thick where most of my other cases run 0.010 - 0.013". It makes me wonder if getting the correct neck tension is difficult, and if annealing is more critical. The brass is also hard to run over a sizer button (annealed or not), which may also lead to cases slightly out of spec. If I was setting up a rifle where accuracy is the #1 priority I would go with a neck turn and turn the cases down to a more normal thickness, and use bushing sizing dies.
Thanks for the comments. Yes, my Lapua brass is about 0.013" thick in the neck, so 0.021" is thick. Neck turn would probably be the ideal way, but I look forward to neck turning like a root canal at the dentist. Also, trying to avoid the custom reamer route, so it may come down to what reamers are out there. To some degree you can improve the neck tension issue by using a bushing sizer to get the ID just slightly undersized, and then open it up with an over sized (0.2640") expander ball. But, if thickness is highly variable or not concentric then it starts to get difficult.