IHL,
Pressurized Aircraft DO leak, and actually quite often, its just not a problem since the leak is usually outwards due to the pressurized cabin.
One of the Beechjets I used to fly, had this constant whistle like sound which we figured out came from the door seal which wasnīt inflating properly, another Beechjet, rain provided started leaking from the overhead panel once the pressure diferential matched on descent at around 8,000 FTAMSL. These were almost new aircraft.
Donīt think the tiltrotor will be much different.