I still don't think this argument holds any water, though, because ultimately - who will end up wearing the clothes from the collection in real life, anyway? - most likely grown women, since that generally tends to be who can afford to wear runway designer pieces. Plus, aesthetically, it's often very interesting to have an "older" model wearing something "younger" as it creates a visual tension of sorts...it'd be boring if "young" collections could only be worn by the "young." That's a very one-dimensional way of thinking, and not particularly clever, either.
The same argument popped up in Madonna's Versace campaign thread, too...about how it was such a youthful collection and therefore needed young models...which is just silly, really (especially because what designer ISN'T designing collections that are supposed to come off as looking youthful? Who out there is designing with the intention of making women look as old as possible??). Ultimately, it doesn't matter how old the person is in front of the camera, it just matters if the results look good or not. I'd say in this case, they don't look that good. Uninspired portraits, made even worse with the HORRIBLE addition of the tumblr-esque landscape shot. So pretentious.