A4, we're close to the same page I think.
Pressurisation loads would help to stop "inwards flex" to which a yacht hull is terribly susceptible. As I see it, the loads would tend to be mainly in two dimensions and the hull would not have "in and out" loadings. Think about the loads in a multi flying a hull or close to it - think of cross beam stresses and attachment stresses, then slam into a wave and dump both hulls into green water, slowing to a couple of knots while the rig is doing 25Kt plus instantaneously.
When a hull fails at speed in, say, the Southern Ocean, it is not a simple ho hum hop into the life raft. You are very likely to die and quickly. Exposure will do for you within minutes in winter and tens of minutes in summer - lose the boat and you're screwed.
A little bio - I have been racing high performance multi hulls for decades and also have mega hours on big Boeings as a maintenance guy, flight engineer and pilot from B707 up to B744 so I really do know about aircraft and flexing.