Section 3.1.4.1 - Is there some way to define a sequence and then re-use it in several "anchored sequences"

Yes, it can. Added language to the start of 3.1.4.1 to make this more explicit. A Sequence becomes an Anchored Sequence whenever a single Interval within the Sequence is Anchored. An Interval is Anchored when it has a specific starting date and time (dtstart). A Sequence may become Anchored when a Designated Interval becomes Anchored through Binding its Inheritance. A given Sequence may remain Unanchored while being incorporated into many Anchored Sequences through multiple Gluon references each creating a different Bound Start.