As you point out, KBLB has not indicated specific markets or products that differentiate between MS, DS, DS2.0, and Pure Spider Silk (PSS).
If they would say something like, "MS is intended for technical fabrics; DS 2.0 will see its first applications in military tactical clothing, and PSS is intended for ballistic applications," then we would understand the differences between these kinds of silk. But nowhere do they specify the particular markets for specific lines of silk.
It's a secret. Why? No idea. But a secret nonetheless.