I agree that "DS" had multiple meanings, but in practice I don't think it was really a disruptive system. I DO think DS was a blue ocean system, but I don't think it was disruptive. (Basically the opposite of my views on Switch.) Disruptive products invade and take over existing markets even if they start in a new one. What market did the DS invade? The generation 6 default for the handheld market was that GBA was the only viable handheld. DS didn't disrupt the handheld market, but it did grow it a whole lot and at the same time it wasn't really competing with the PSP because it was also fairly successful. That means it was a Blue Ocean product.
3DS on the other hand was a red ocean product. Nintendo cut the price by $80 within the first year. That is red ocean behavior. The philosophy behind the Blue Ocean Strategy is that you make more profits because you don't have to cut the price or add expensive features or other costly things that products have to do when they compete directly. 3DS defeated the Vita, but it didn't make good profits while doing so. 3DS was neither blue ocean nor was it really disruptive.
I know 3ds is red ocean product. But the effect the DS is so strong and reverberate in the next generation. I believe the DS is both: a blue ocean and a disruptive product. Cheap price is the key feature here. Nintendo DS is a cheap portable and good enough, likewise disrupite products are.