Interesting -- do those wireless cell phone chargers cooperate with the phone first, to be sure it's a phone on top of them (and not a wallet with credit cards with magnetic strips, for example)? Hopefully they have that feature...
yes, the main board which located in the USB plug can identify the signal.
First, the electromagnetic signal will establish a handshake with the mobile phone signal.
The motherboard can identify the current mainstream mobile phone models
Then, according to the specific adjustment of the mobile phone to charge accordingly.