If you get twice as much work done by 10 people as 5, you need to think about what the new people brought to the table, or the old ones don’t.

If the team didn’t have a facilitator, for instance, some team members may not be coordinating, causing issues with finishing tasks.

Because despite having a factorial increase in communication paths, you still got twice as much done? Are you sure?

You have to ask these questions because at worst something bad is happening. At best someone new brought in new techniques that work better than your old ones. You need the answer in either case.

This doesn't make sense to me. Adding more people add communication overhead so you would get sub-linear return. I don't see how you can even expect more than linear return.