Cocktail party facilitation

A common ground rule for facilitated group sessions is "one person speaks at a time".

The rationale is that it's easier to understand a single-threaded conversation, it addresses people being interrupted, etc.

I wonder if, at least in some cases, this rationale is flawed.

Single-threaded conversations are unnatural because they imposed a centralised structure.  How might a more natural, decentralised facilitation approach look?

What if your group session was facilitated like a cocktail party or other similar social gathering?

People would have conversations based on what they want to talk about with whom they want to talk to.  Some conversations would be more dynamic, even heated where others might be more relaxed.

There are some problems with this.  How would we collectively learn about what each group talked about?  What about people who don't feel comfortable participating?

Some kind report-out would seem reasonable.  I'm also sceptical that anyone uncomfortable participating would not also be uncomfortable in a "one person speaks" scenario.

Perhaps this all comes back to Open Space and World Cafe style approaches?