The feedback we have received many times over doesn't support the above assertion. When we put out 9-Max MTTs in Omaha variants, the feedback is loud and frequent, asking us to change them to 6-Max.
You sound like someone who writes for Vox here. Just because the majority of people you talk to and hang around believe in something, does not mean the majority of people do.
The entrants in 6 max (especially 4 max) are lower than in 9 max with the exception of low buyin NLO8s. You are clearly just listening to feedback from select regs, and missing the greater picture. It's like this on every site. As a pro we also like ante only and mixed formats, but recs don't. As a former room manager, we like as much float. We don't care so much about regs who only deposit for the guarantees.
6 max is in Omaha is a completely different game than full ring. It's good to have both certainly. For pros, there is a greater edge due to the nature in preflop edges. 6 max encourages more preflop pots, and since hand values run close in value, there is more variance in outcomes, unlike NLHE. In 9 max it's post flop, and far greater edges post flop than in NLHE.
The other comments to grouping like events together I second. Synergy exists between events. It's good to have a holdem and a mixed game event each day like at the WSOP.