Ok, I think I found the direct answer to Concensus.
config system global
set virtual-switch-vlan disable
This would change the GUI to show "Hardswitch". And you'll get a warning below:
labtest60f-1 (global) # set virtual-switch-vlan dis
This change will disable trunk on interfaces and remove VLAN from virtual switches.
If you don't want it to be changed, type "abort"
I need to test further but based on the description for 300E below, it appears that if you enabled this (it's enabled by default at least 6.4.8 on FG60F) you can create virtual switch interfaces per VLAN, like port 1-2-3 for VLAN10, port 2-3-4 for VLAN20, which simple hard-switch can't do. I still don't know what "set trunk enble" on each interface would do.