Only the basic communications protocols are covered by the " Standard" in order to ensure interoperability and backward compatibility with existing systems.
The "Standard" defines the signal sent over the rails, the tolerances allowed in its generation, the tolerances that must be accepted by the decoders and the basic communications protocol used to convey information to digital decoders.
Recommended Practices cover things like the locomotive sockets and "advanced" decoder features.
Manufacturers are free to design and implement DCC hardware and interfaces that make sense for their customers.
Manufacturers are also free to define how the DCC packets are handled by their system whether it be a simple command bus or a sophisticated network topology.
Digitrax has moved beyond the simple "Standards" to incorporate many features never contemplated by them. Digitrax Complete Train Control incorporates compatibility with the "standards" and "recommended practices" to allow for interoperability with other manufacturer's products. Digitrax Complete Train Control offers additional high level featuers such as detection, signaling, transponding and more.