The factory PTI system currently has far more features "cradled." Yes, it works over Bluetooth... but it really is more limited than almost any 3rd party kit I've seen. But, you are right, LR/Nokia could just give up.
Here is a feature summary I posted elsewhere...
Factory PTI over Bluetooth is fairly basic:
1) Obviously, answer and drop phone calls.
2) Store and dial voice tags and phone numbers in the LR3's voice recognition system.
3) Dial "live" by speaking the phone number.
4) Dial phone numbers (or generate touchtones) using the keypad on the radio head unit.
5) See the phone number of the caller on the stereo head unit (not the name).
If you have a phone connected via cradle (not Bluetooth), you gain:
1) Browse your actual phonebook and calling log via the radio head unit.
2) Display the name of the caller on the display (if entered in your phonebook.)
3) Display signal strength.
4) Charge your phone.
5) External antenna.
6) Turn off your phone from the head unit.
7) Call Waiting support. (Answer 2nd call and switch between them using PTI controls.)