The text certainly implies they are, but there is no formal compliance point.
Proposal: Change the last paragraph in 4.1.8 as follows
Old:
The Sequence of a DataObject corresponds to the XML elements representing the values of its properties. Updates through DataObject, and the Lists or Sequences returned from DataObject, operate on the same data. Returned Sequences actively represent any
changes to the DataObject's values.
New:
The Sequence of a DataObject corresponds to the XML elements representing the values of its properties. Updates through the DataObject API, and though the Lists representing multivalued properties MUST BE visible through the DataObject’s Sequence, regardless
of whether the sequence object was retrieved before or after the updates were made. [
COR04010802].