I looked at the first two or 3 to finish. After your comment I went back and checked. I see one F50 from ‘87 and an Orma from ‘90 in addition to lots of cruising cats. I also see that the average skipper age of the multi class seems to be about 60 years old. The age of the Class 40 skippers seems closer to 35 years old. I think the Class 40 seems to be a pro circuit, the Multi class seems to be a French version of the ARC. Its the same phenomenon with Use It Again. I think it’s best explained by the age/skill of the sailor in the respective classes and the boat‘s age/purpose.Did you even look at the Rhum Multi entry list?
Plenty of high performance multis including ORMA 60's but more specific to the question - a state of the art, foil equipped, carbon, 40' tri that is currently out there upside down and was days behind the Class 40's before it flipped.
So why do you think that is?