Tbh, I think head hopping it what people use to describe omni done badly - that is popping in and out of heads so fast the reader's neck gets whiplash. Or done confusingly, so the reader can't be sure whose head they are in at any given point. It's not moving from one head to the other that's a problem. It's doing it badly.

Omni feels like it should be easy, and it is easy, to an extent. It's harder to get right though, harder to do well.

Look at say Prachett. His Discworld books are all in omni, and it's something of a masterclass. You always know whose head you are in, and are always aware that the voice is of the narrator (a vital part of omni). If he switches from one person to another in a scene, it is done with maximum finesse, seamless, and it's not just a quick jump. It's never confusing (unlike that book I read where the POV shifted three times in two short sentences, leaving me with a 'huh? Who...what?' feeling. That's headhopping)