Does the 'iPhone' label on a Contact's phone number enable any special handling?
The iPhone label does not provide any special handling instructions or added features of any kind.  It's a purely aesthetic touch that only impacts the display and voice dialing of a contact's number in the same way any other label does, such as "Home", "Work" or "Mobile".  

If you are looking for further information on how the iPhone does provide special handling for other iPhones, such as iMessage and FaceTime, there is a great thread, right here on Ask Different, that details just how the iPhone, in conjunction with Apple's servers, uses the UDID and Apple ID associated with the device to provide all those special iOS only features.