TRANS13 — Any in transaction context?

the PropagationContext structure contains a sequenct of parent identities,
followed by an any "implementation_specific_data".

This seems strange. Why do we have a single Any if we can have any number
of parent identities, which could conceivably span vendor boundaries?

It seems that what would really be required is something like this:

struct ParentInfo

;
typedef sequence<ParentInfo> ParentInfoSeq;

Could someone help me out here? I don't see how a single any could be
sufficient if there is to be at least a theoretical chance of interoperating
across vendor boundaries.

resolved, see below