I have a 2007 Southbay triple toon and have spoken to the hull designer often about this as it came with air valves in each of the sections. I was getting ripples in the nose cones (This is a 60mph pontoon) and was concerned about it. He stated because of the speed of the boat it takes more abuse than a standard pontoon would, the air pressure helps to keep the toons in shape. They recommend 4lbs in them standard which I had been running. He told me to bring them up to 6lbs I did this last year but it did not seem to do anything but after a summers running the ripples are gone. I assume it took time for the aluminum to come back to shape.
My point is it seems the pressure from the inside helps the toons keep their shape not that, that is a real issue but even for ones that run on lakes that see bigger waves it might be of advantage. My old pontoon had vents. After 19 years of running it had small deformities in the lower nose cones that never really bothered my but I wonder now if I had pressurized those if those would have formed.