but on other aircraft the nose gear is mechanically prevented from turning more that 50 - 60 degrees
It's yet too early to speculate about why it turned to 90° but it's much better to have it that way than less. Imagine what would happen if you have it turned about 10-20 degrees...!
It's pretty obvious to me that Airbus designed this part the way that it goes to about 90° so it doesn't turn into a catastrophic position.
Modern aircraft also have the feature of locking it out and letting it go more than 90° for towing, including Airbus.