UPSTREAM_COMPONENT_INTERFACE_ID question

["Saha, Sayandeb" <ssaha@netplane.com>]

Kireeti,

draft-kompella-mpls-bundle-05.txt (section 5.2.1) speaks about the
UPSTREAM_COMPONENT_INTERFACE_ID object which is to be
included as a part of the <sender descriptor> for bidirectional LSPs
when using Explicit Indication by Unnumbered. This seems to be an
exception which allows one to specify a component for the upstream
traffic.
Specification of a component for upstream traffic is not supported for
other indication types in Bundling (Implicit Indication and Explicit
Indication by IP address), but instead is inferred.  Also in the
non-bundling
case, when signaling unnumbered interfaces, the ERO only includes 
the upstream router_id and the outgoing interface Id, again nothing about
the upstream link on which traffic should be carried.

My question:
What is the point in having a UPSTREAM_COMPONENT_INTERFACE_ID
for the Explicit Indication by Unnumbered case, when there is nothing
similar
for other cases?  Isn't the  DOWNSTREAM_COMPONENT_INTERFACE_ID 
enough to let us know which link should be selected for reverse direction of
the Bidirectional LSP? Am I missing something here?

-Sayan