No Digi mesh does not do a scan channel and channel selection. That part is left up to you to perform using the AC, SC and CH commands.
Yes there are differences in ZigBee and Digi Mesh. Zigbee is a international standard where as Digi Mesh is not. Zigbee is a tree type mesh where as Digi Mesh is a true peer to peer mesh.
The channel scanning function you are referring to only occurs upon network configuration on the first power up. Once the network is formed, it will not change channels unless told to do so form an outside source.