@tendertouchThat's true, as the whole one speaker per paragraph is based on the One-Subject per paragraph, as in dialogue, the speaker is the subject of the dialogue, as they're the ones speaking (thus the subject of the paragraph, not the commentary).
It's a fairly nuanced aspect of writing, which is why it grates for so many new writers.
That said, I've also done the "at the same time" response, yet I restrict mine to things like crowd noise or press interviews where the questions/shouts come fast and furious, where the character often can't tell who's specifically asking which question, thus they tend to hit like a wave, washing over the character who's left wheeling as a result.
I've used that particular approach quite a few times, including several in the same story (after all, how many fictional chapters have to fend off conferences.