I dont find this legislation that bad. Essentially I guess they wanted a way to make using GPS on your phone legal, but without giving everyone the ability to send text messages and say they were using their GPS. Built in GPS units dont have text messaging, so I would hazard a guess thats why they are listed seperately.
If you answer a call on a mounted phone its a single button press, so its unlikely to get mistaken for texting. If your swiping away at a text message or entering an address while driving, expect to pay the price
Its fair enough, sending text messages or browsing the web on your phone while you drive is distracting.