I assume it has something to do with the following part of MaidSafe Dev Update - January 25, 2018
One important thing that comes up while tweaking the parameters is the average and peak section sizes. While the average is pretty good, the peak sizes sometimes make us wonder if we could be more efficient given those many nodes in a section. Currently, the Elders are all connected to every peer in their section and the swarm strategy is O(n^2) for votes and blocks. We will also be deeply looking into secure gossip and finding out if we can design a system which addresses both: not forcing connection among everyone (thus frugal use of socket descriptors) and also making swarm ideally logarithmic.