Yes, once you create the virtual switch/sensor, Approve it for use by Echo, and discover new devices from Echo, then the virtual Device shows up in your Alexa app just like all your other SmartThings devices. Echo doesn’t know that it’s virtual.
So you can then go ahead and create your routine to trigger off of that virtual sensor instead of triggering it from the real sensor.
Because the virtual sensor doesn’t really exist, you have to have an automation turn it on to make activated. That’s why it’s convenient if it also looks like a switch because those are very easy to turn on and off.
Now you use the official smart lighting feature and you say when the real motion sensor turns on, turn on the virtual switch—but only between those two specific times.
And you Will have the switch turn off after inactivity.
If you want to get even more complicated you can, but you will probably have to use something other than the official features: see the following FAQ: