3.5k 1x1 mode has its own advantages though.
1. lens compatibility. super 35mm cine lenses, efs lenses, in addition to ef lenses.
2. dual iso. some mlers reported that he made 2 hours of 3.5k 1x1 footage with dual iso, without noticing any purple fringe. this is solid field test.
3. a tiny little bit higher resolution.