The on-board LAN 9514 does have a WoL output pin but it does not appear that the chip remains functional and can detect a WoL packet when the Pi is halted and definitely won't when the Pi is powered-off.
USB network adapters connected directly to a Pi will not work because they don't have a separate signal out which can be used to reset or power-up the Pi. They can only tell the Pi they have received a WoL packet via USB. So, even if they are able to indicate receipt of a WoL packet when the Pi is powered up and running, that's not going to happen when the Pi is halted or powered-off.
This will allow a Pi to be re-booted from a halt state -
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.---. .----------------.
| H |---------------[|_ _ Pi |
---| U | .--. |_| |_| |<=== 5V
| B |---[| |----. |_| :::::: |
`---' `--' | `----------------'
WoL | /|\ To Run
Detector `---------' Header
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.---. .----------------.
| H |---------------[|_ _ Pi | .--------.
---| U | .--. |_| |_| |<===| Switch |<== 5V
| B |---[| |----. |_| :::::: | `--------'
`---' `--' | `----------------' |
WoL | |
Detector `------------------------------'