The loss of the ring-to-sprocket splines shouldn't be a problem if the lockring is properly torqued. Since it's a freehub, once the sprocket is pulled forward against the FH body's splines, there's never any reverse torque on it so it won't tend to work the lockring loose. Once tight it should stay that way just as all your other fasteners do. If for some reason it ever does work loose, a bit of rubber cement on the thread would provided the needed traction to prevent a recurrence.

I'm with you on the durability to weight issue though I don't think it'll make a difference here. On the flip side most of the dough folks spend on bikes these days is to save weight, and the big three are in a bragging rights duel. They're scrounging around looking for every gram they can shave to claim the top spot. IMO this is one of the more innocuous places to save, and a better decision than brakes, or other highly stressed components.