Maybe it is just because they don't know what kind of handicap number to give it? If so, you would think they could let it race on an unofficial, "provisional" basis so it can start developing some statistics for a handicap rating in following years. I can see that the race committee would not know how to rate it. But safety reasons? That does not seem logical. As you said, if it cannot go out through surf, it could launch somewhere else and sail to the start line. That particular race is along a shoreline all the way and seems to be accompanied by lots of powerboats all the way around the island, so it's probably safer than most distance races. No?

Do they allow monohulls? Do they allow trimarans? Do they allow multihulls with foils?

I've never seen the Notice of Race, so I don't know if it is specifically limited to "catamarans." But if it IS limited to catamarans, it probably does not say that both hulls have to be the same length.

All people who put on distance races are increasingly going to have to deal with technological advancements by deciding whether to discriminate against the new-and-different or whether to let it be a part of the process of evolution and survival of the fittest.