Would love to hear more thoughts on this as well. I had similar impressions with the Ether C.
The Ether C lacks mid-bass. Subbass is great once broken in. The Ether C Flow adds more midbass and mids, filling out the previously "thin" parts of the sound. It also smooths out the treble appreciably. I prefer one black pad on the Ether C 1.1 but none on the Ether C Flow.
EDIT - To be clear, it's still not at Ether 1.1 levels of mid-bass. But it no longer feels thin.