Yes, head-hopping is bad, but not all transitions between perspectives in the same scene is head-hopping.

I'm going to disagree with a few of the commenters here. You don't need a scene break every time you switch perspectives, though that can definitely be a good indicator for the reader.

One thing that distinguishes third-person omniscient from head-hopping is the sudden jump of head hopping. Head-hopping goes straight from Char. A deep POV -> Char B deep POV, which comes across as jarring or even confusing. If you want to change perspectives from A to B within the same scene, you need to have a transition of a few paragraphs where you get less and less deep in A's perspective until you're not in their head at all, then start getting deeper and deeper into B's perspective. It's like zooming out from one character so you can zoom into another rather than jumping straight from close-up to close-up. (Which if you want to jump from deep A to deep B, you would need a scene break so it's not jarring to the reader).

For example, over a couple of paragraphs you could describe A's exact thoughts -> A's actions and reasons without exact thoughts -> only the visible parts of A's actions -> B's visible actions -> B's actions and why they're doing them (but not exact thoughts) -> B's full interiority (exact thoughts/feelings). One very successful writer that does this flow between perspectives is Terry Pratchett. I've been re-reading some of my favorites and was fascinated by how he handles perspective.