Actually it's not they only discuss two modules being added.
Dual Channel Memory Configuration This motherboard provides two memory sockets and supports Dual Channel Technology. After the memory is installed, the BIOS will automatically detect the specifications and capacity of the memory. Enabling Dual Channel memory mode will double the original memory bandwidth. The two DDR4 memory sockets are divided into two channels and each channel has one memory socket as following: Channel A: DDR4_2 Channel B: DDR4_1 Due to CPU limitations, read the following guidelines before installing the memory in Dual Channel mode. 1. Dual Channel mode cannot be enabled if only one memory module is installed. 2. When enabling Dual Channel mode with two memory modules, it is recommended that memory of the same capacity, brand, speed, and chips be used.