Good diagram, but I think it might be misleading for the subject at hand. Although the Zigbee protocol is frequency agile, SmartThings’ implementation is not. Whatever frequency you are randomly assigned is what you got (which can be verified in the IDE, My Hubs). In my case, the hub is on Zigbee channel 15. Although it’s between channels of the 2.4 wifi band, because the signals are not zero bandwidth (typically 20 MHz), I still have to avoid that part of the spectrum on my router.
(Edited the reference to wifi channel avoidance; I misread the diagram first time around. 
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