You are sort of making my key point.
ISAF has not stated exactly what the key feature is.

TV appeal? (Big... Bigger the better = Tornado
State of the art sailing catamaran? = F17 with curved boards
Laser equivalent. = Hobie 16
Modern design but affordable. (All of the F16 flavors and a Tiger)

My take home from the sailor reports is that ISAF gets to pick between these 4 philosophies. with the Viper coming out of the trials as the choice of the F16/F18 flavor.

Obviously they don't want to tell you what the top objective is... This Keeps the options open. On the other hand... the cat world will scream at the selection this way....