Jake, the criterea were not in that article but if you follow the links you eventually get to

http://www.sailing.org/technical/MhullInvitation03.pdf

I think what the ISAF are trying to do is get a boat that finds the best sailor and so accesability is the most important thing, or in other words picking a boat that in thier view will get the most people on the water.

I think they are trying to keep cost down and not make the boat intimidating, which cats can be.

Although the boats will be supplied for free at the events, the best crews will inevitably be those that practice on that particular boat, and so they need an accesable boat not an elite boat that only a few can afford.