Also, the centerboard and rudder are foam-filled composite that float. So if they kick up from a grounding or impact, they pop up pretty fast and that lessens the damage to them.

I don't think this is about multis in general. This is a maker-specific set of design features that Quorning has designed into most of the Dragonfly models. Several cats I've looked at can't even handle a gentle grounding. For example the Maine Cat 41 which has spade rudders and saildrives forward of them, and no keel so there's no protection forward or below. I've been told by an owner that the rudders aren't designed to support the weight of the boat. So what happens if the tide runs out at anchor or a shallow slip? That's a show stopper that would keep me from buying one of those. Shallow draft capability should be a feature in a multihull, IMHO.