The generic payload can be extened on a a custom basis and intermediate bus bridges and routers can be polymorphic about this: not needing to know about all the extensions but able to update timestamps to model routing delays.
It also defines memory/garbage ownership and transport primitives with timing. Finally, it defines a raft of useful features, such as automatic conversion between blocking and non-blocking styles.
However, TLM 2.0 it is a bit too complex to get a deep understanding of in the time available for the Part II course, hence the motivation for the 'Toy ESL' practicals in TLM 1.0 style.