No, actually it could be helped. It'd just be harder. That they don't do it doesn't mean it can't be done.
Just because Funi chooses to put all their voice actors in a soundproof closet doesn't mean they have to. The Japanese use the whole ensemble in one room as do, again referring to Batman: TAS, a bunch of western shows.
It is less convenient because you have to get everybody's schedules to fit and it's probably more expensive (at least to start), but it's also a superior way to do things.
Yeah but for whatever reason anime is not dubbed that way in the US. All the companies record people apart. That's how they do it, even if it sucks with group scenes like this.