ohhhh you're my hero!! Thank you!!
I totally forgot I had this enabled from the "Shrink Array" guide.
It was actually showing as "All" in the UI, but I selected the new Disk1, applied it, then deselected it again to include All, applied it. Started Array and now the shares are showing up! Seems like the UI has a bug here, or at least shows "All" even though an old & now unassigned Disk is still selected.