I can't find any detailed information for the following CLI commands. the CLI reference seems to be missing some key configuration details.
rf-virtual-mode under the essid configuration
rf-virtual-mode under the interface Dot11Radio configuration
I can share the latest CLi reference guide if you like, (I have 8.2-4) however you're right it doesn't seem to make reference to the rf-virtual-mode, however there are only 3 options in terms of the ESS profile.
NativeCell - All Ap's are independant and have have unique BSSID. Typical micro cell like other vendors
VirtualCell - Single channel deployment, all APs share a common virtual BSSID. Allow seamless roaming and other nice things.
VirtualPort - Single channel deployment, each client device gets its own unique BSSID. This RF technology was replaced by VirtualCell - doesn't work with Apple iOS Mac randomization.
This is the same for the when you are in the context of a Dot11radio Interface.
Hope this helps