A DESCRIPTION OF THE PROBLEM :
Documentation hasn't been updated for JEP431 (Sequenced Collections) so doesn't include SequencedCollection, SequencedSet or SequencedMap:

- Collections Framework Overview API documentation https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/doc-files/coll-overview.html

- Outline of the Collections Framework https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/doc-files/coll-reference.html