I was musing over this very thing a few days ago, after viewing many Menefee, Hampton, and Bose shadow pattern knives. I know that shadow patterns go back many decades, but these - the ones I've seen anyway, have bone or wood handles, or even nacre. But these new customs all feature modern handle materials; micarta mostly, but also G10 and carbon fiber.
That's where the line blurs for me. Yeah, OK, I'd still call a shadow micarta slipjoint in a stockman pattern a "stockman", but while a stockman is a "traditional" pattern, I'm hesitant to call that knife a "traditional knife". Some might not have a problem still calling that knife a traditional knife, but as others have mentioned, where then does the line get drawn. I understand why people wouldn't want to include the Stag Kiwi (or bone), since its lineage isn't from traditional patters, but rather from modern (aka "tactical") knives. The UKPK and its siblings are even further away from the traditional lineage.
Handle materials aside, another point of contention for me is the lack of bolsters. In the vaguest of definitions, a traditional knife - to me - has bolsters. But obviously not every traditional knife has bolsters, nor is every knife that has bolsters a traditional knife (like Blues' Carson above). Bolsters were ubiquitous with traditional knives because the pivots needed bolstering. Modern knives, with modern materials and precision machining, don't really need bolsters. These days, bolsters on a modern knife are mostly there for style. Knives like Emersons and the Spyderco Military are proof of that. Which leads us back to the shadow pattern knives. With hardened steel (or even titanium) rather than nickel silver, and epoxy laminates instead of brittle bone, bolsters aren't really necessary anymore, at least for strengthening purposes. Because of this, I'm again hesitant to classify such a knife as a "traditional", since it doesn't need or use traditional methods of construction to be a solid tool. Only the blade selections, being the same as other traditional knives, keep them in the "traditional" category.
If others whom are more learned than I say they're traditional, then I suppose I'll go along. I'd like to use the adage "I don't know, but I'll know when I see it", but like the OP, when I see these shadow pattern modern material knives, I don't know even when I see it. I'd be more inclined to call it a modern interpretation of a traditional design.