@GIDDION Thanks for yet another helpful post. Yes it was quite a job to persuade our almost unmodified upstream Anakonda installer to get the results we were after. Hence the double install procedure and strange defaults etc. Hopefully as btrfs, grubby, grub, et al develop we can move to a more btrfs native arrangement raid wise on our system disk. But in the mean time this does appear to work, all be it in a rather long winded double take type fashion.
@Spectre694 in the following forum thread seems to have gotten to the nub of the current upstream holdup on this:
As per your suggestion I have opened a new issue in the rockstor-doc repo with your exact recommendation:
Thanks for your diligence on this one and glad you got there in the end.