I see the light Tom - I am no longer confused - it's Marketing!
My guess is the idea is to capitalize on the Circus thing, with minimum investment:
- Series of cars with Circus graphics, based on existing tooling for collectors.
- Semi-prototypical trainsets that give the "flavor" of the current Red Unit
and "runner packs" to extend those sets
Probably little or no new tooling, and a bunch of resin "circus loads" for the flatcars.