In Rapid Spanning Tree Protocol (RSTP), there are several port roles that determine the behavior of the port in the spanning tree. The roles include root, designated, alternate, backup, and disabled.
The discarding state is associated with the backup, alternate, and disabled roles. In a stable topology with consistent port roles throughout the network, RSTP ensures that every root port and designated port immediately transition to the forwarding state while all alternate and backup ports are always in the discarding state. Disabled ports are also in the discarding state.

"The ENCAPSULATOR does not change the inner IP header, except to decrement the TTL and it remains unchanged during its deliver to the endpoint" - only router that encapsulates the inner packet decrements its TTL - during transit, the inner packet is unchanged.