TwinSnakes007
I'm probably gonna regret asking this but, what distinction is this new part of the USD spec. making?
I'd say it's not strictly a USD thing, but rather a Hydra thing. There's never been anything stopping people from authoring USD that has a PointInstancer with light prototypes, but that's historically never been translated through Hydra such that the renderer sees it. There are a few things with lights like that (i.e., USD that you can author which doesn't translate through Hydra).
From a renderer perspective, Lights cannot be "instanced" in the technical sense...
I'd be tempted to say "depends on the renderer", but I'm not sure it's important either way to what follows.
...and Reference already allows you to basically "copy" any USD Prim.
Yes. And perhaps for the *renderer* that's good enough. For working with the USD Stage, it might not be.
My user-story for this is a nighttime helicopter shot of a busy downtown city with thousands of cars with headlights & tail-lights. There is a noticeable performance difference working with a USD Stage that has 1 PointInstancer prim vs 10000 reference prims.