That's not what's being said, I'm referring to coverage issues in home theater (3.1 and above)
Say you have a home theater with a dedicated center - this is used for dialogue 99.9% of the time. Intelligibility of the center is critical for movies. In-spite of this many living rooms (IME), especially those with lots of seating for children/visitors, have seats far enough off-axis that even some of the best traditional designs have a non-trivial drop in SPL. As such, even if the content is the same the level difference can result in intelligibility issues. This results in complaints regarding volumes from those on-axis v. off-axis. Differences of 3dB can cause potential intelligibility issues, so trying to maintain SPL across seating is a consideration.
An omni design simply helps alleviate this SPL drop. A good 3-way can mirror the spectral content off-axis well, but the SPL may not be sufficient for all viewers. Effectively it becomes a coverage issue. Rooms that have seating at severe angles, with people unwilling/unable to adjust seating for better coverage, may find a solution in omni designs. When I sold my Mirage's it was to a family with that exact use case.
Obviously since I sold them I prefer other designs, but horses for courses.
Sound reproduction can make or break movies. An original score for a climax, an action scene that demands full bandwidth and placement, a chilling monologue from an antagonist. I've had a range of displays, but even those that weren't great I could enjoy. The sound was infinitely more important to me. Good sound to me allows a higher degree of immersion.