Why A mesh network is built from many nodes that each relay traffic, and the routing protocol constantly maps which neighbors are reachable. Because there is usually more than one path between any two stations, the network can route a packet around a node that goes off the air or loses its link. That self-healing, multi-path routing is the defining feature of mesh networking, as opposed to a single fixed repeater or point-to-point link.
Watch out The idea that links between nodes can use different frequencies and bandwidths sounds plausible and is possible in some hardware, but it is not the characteristic the pool is testing; adding nodes also does not raise signal strength or reduce out-of-band interference, since each node is an independent low-power transmitter.
Mesh = many paths. Lose a node, the packet just takes a detour.