it's very windy on the open ocean.

if the floor was solid the only place for all that wind to go would be through that poophole.

by making the floor slotted the design lowers the wind resistance and allows it to pass through, thus equalizing the pressure inside the room vs under it (think of it like a balloon).

also because of the small size of the hole, should the floor be solid, the pressure is increased.

this could be resolved by attaching a pipe the same size of the hole that sticks out of the bottom between 6-8 feet. I assume they didn't do that for maintenance reduction. though, this wouldn't stop sheer winds from shooting up the pipe.