На сколько я вник, это обычный overlay mesh поверх STA + AP
Ну да, не стали велосипед изобретать, а сделали свой исконно-посконный из того что было под рукой.
However ESP-MESH allows nodes to simultaneously act as a station and an AP. Therefore a node in ESP-MESH can have multiple downstream connections using its softAP interface, whilst simultaneously having a single upstream connection using its station interface. This naturally results in a tree network topology with a parent-child hierarchy consisting of multiple layers.