I read somewhere that the 6 speed box doesn't have the torque capabilities required to run with that engine, especially in SS spec, as it is esentially the older 5 speed box with extra ratio on end from the FIRE engined cars which didn't have anything more than 99bhp 96lb ft, so asking it to transfer over 200lb ft in SS spec Punto is asking a lot of it. Even the box casing is same except for the longer bolt on end section to accomodate the 6th gear. Having fitted one to a Seicento with 1.4 16v engine have had the 5 and 6 speed boxes sat next to each other its remarkable how little was actually changed from the box fitted to the 60lb ft cento box, very clever TBH, must have made for very little in terms of research and development making huge cost savings.
So it uses an Alfa box, which makes you think why did they not fit the Alfa Q2 diff as its silly cheap to buy from Alfa even as an after market item and could have make the car even better.
Though as the car has fully integrated Bosch management system which work everything from ABS, to stability control, Air-bags, to even the headlamps maybe having a mechanical diff would have meant longer development time trying to integrate it with the Bosch system.
Once car is actually out there in public domain and people start to play with them more becomes apparent.