For Boeing and McD a/cs, the nosewheel is mechanically linked by cables to the nosewheel tiller. So, if there is a movement of the nosewheel, the tiller would move even if the bypass pin is attached. The bypass pin physically deactivates the steering thru the hydraulic lines.
For Airbus, the "FBW" system is used for the nosewheel system.. The bypass pin actually sends an electrical signal to the BSCU which needs certain conditions to be met like eng on before it activates the nosewheel steering thru the tiller and rudder pedals. The rudder pedals can even be deactivated thru the tiller. Turning the tiller actually sends electrical signals to the BSCU which is converted to mechanical action thru thr servo valve.
Hope this helps. Have the pics, but don't know how to paste it here.