Yes, in effect that's what my 2nd answer was saying, though not in the same words.
I'd submit that the more interesting dosing for a CTLA-4 combo is not treme in MYSTIC -- which follows the traditional "up to 4 doses" schedule that is standard for CTLA-4 inhibitors; in effect, AZN isn't doing anything out of the ordinary with using only 4 doses of treme in MYSTIC -- but is Yervoy in CheckMate 227.
As you alluded to (which I didn't realize) Yervoy appears to be dosed continuously, every 6 weeks. Seems to suggest that BMY thinks you may need to "re-release" the brake for 1L NSCLC, though less frequently and with less intensity (i.e. lower dose) than for CTLA-4 in other tumor types.
We should have the answer to which approach is better fairly soon, but it seems like BMY has generated more robust Phase 1 data to inform its Phase 3 design. If I was invested in AZN, I would definitely be worried about MYSTIC...
