That is silly. That would mean that fashion could never have style and style could never be in fashion.
As I mentioned above, I think those terms are wrong, but the concept is good. Maybe 'fashion' and 'good-design' might be better ways of looking at it.
Fashion follows fancy (i.e.: what the 'trend setters' fancy at the moment). It might involve good design (in those moments when the 'trend setters' recognize and value good design), but often doesn't. In fact, often, it embodies the anthesis of good design in an act of rebellion from the 'norm' (when the 'norm' is based on, or involves good design).
Good design, on the other hand, is by nature timeless (within limitations)... because it's good design. It might look a bit different over time, but has certain fundamentals to it. The change in look or function often fall within real-world limitations and are driven by need to solve some problem... thus it will ultimately change over time (as needs drop away, or limitations change).
In that regard, I suppose the candy iMac was at least in part, good design, as it was the 'all-in-one' computer of that time, within certain bounds of that time (yes, the candy colors, were more fashion). Today's iMac follows that lineage, but looks quite different because of technology and materials advances. But, it's similar at the core, and is different from many other all-in-one computer designs that aren't nearly as elegant.
Or, say a car... the basic or core 'look' and 'feel' haven't really changed for quite a long time, while the 'fashion' of cars has changed considerably. And, if you diverge too far, you end up in bad design land quite quickly.
Or, since the fashion runway is the topic at hand.... a 'suit' or 'dress' are fairly timeless designs, while 'fashion' come and go as quickly as these runway events.