That is true, but unusual, based on research. However, those people are compatible with quiet offices because they can blast headphones, or talk at the coffee maker, or hang out in people offices/cubes and bug them. So quiet areas are not designed for loud people but are totally "loud people compatible". On the other hand quiet people (the majority) dropped into a loud open plan, are not compatible.

I've never seen or worked in an open plan that doesn't have private areas for the cool kids and bosses either formally or informally. Perhaps a site like that exists. They are apparently rare.

Background noise and activity isn't all alike. In a coffee shop it's irrelevant: strangers moving about and talking about things that don't concern you. That's easier to tune out than things than the noise and activity in an open plan office where it's people you know moving about and talking about things that may be relevant to you.

Also, people are different -- some are better able to tune out background noise -- and the same person is different on different days and while doing different tasks.

Yes, very much so. This is why in grad school, I did a lot of work at a bustling coffee shop rather than in our open-plan office space. I had a much easier time concentrating at the coffee shop; there was more activity, but none of it was relevant to me.