Great article about the inner workings of the network. Just 2 remarks:
What you call group is now called section. See the change of terminology in MaidSafe Dev Update – December 6, 2016. A group is now a subset of a section of exactly 8 nodes. It contains nodes that are the closest ones to a specific address. A node belongs to many groups, but it belongs to only one section.
The minimum number of nodes to make a new section is 22 because, like you explain later, a section is split in two only if both halves are greater or equal than 11. Meaning that it splits when it reaches 22 if it is well balanced, but can grow above 22 if it is unbalanced. The margin (11 – 8 = 3) is a hysteresis factor added to avoid a merge quickly after a split.