Virtual wlan2 is indeed piggy-backing on top of real wlan1 on the radio part of it. However, on the router part it's own interface ... and if you want any traffic to pass wlan2, you have to configure the other side of it.
Essentially, virtual wlan is virtual as far as
/interface wireless part of configuration. It's completely indpendent in other parts, e.g. in
/interface bridge. To show that virtual wireless works, you can simply add wlan2 interface as bridge port
/interface bridge port
add bridge=bridge-wifi interface=wlan2
and should work the same way as if connecting to physical interface.
And, BTW, physical interface doesn't have to be active at all times, it only has to be enabled at all times. So if none wireless clients are connected to Lynn91 SSID, wlan1 interface will be inactive. But wlan2 interface with SSID homeguest will still be active if some clients will be connected. However, if you decide to disable physical interface (e.g. because homeowner will not be at home, so no Lynn91 wireless needed), then virtual will be brought down as well.