There's no opus number for this one -- or any of the film-derived concert works. (We listed many of these on another recent thread.) Rozsa did include the many of the these works in his catalog of published music. So I don't think that Avie's distinction is tenable.

It's true that the YB Fantasy recasts the original symphonic scoring for an ensemble of organ, brass, and percussion. Those changes are certainly significant -- but no more so than the symphonic recasting of the simpler film textures for the great Quo Vadis Suite.