Thanks, brendan.
My view is that the Chambers definition refers to the setting of the whole (or substantially the whole) text (as in Fauré’s, Duruflé’s etc), not to a single movement from a setting, but I see your point. We certainly agree on the encore element, which isn’t even necessary for the surface and only adds to the confusion.
Ah well, it’s (nearly) Christmas, so I’ll stop grinching now.