If that culling technique is an automatic process, the boost that can be achieved in both frame rate and level of detail is surreal. And it still doesn't explain the Hellblade 2 demo, because there isn't any occlusion going on there and it still looks like there are no visible LOD swaps even in the distance. DirectML is basically making almost the full power of the GPU available for what you can actually see. Now there are some downsides to this, lighting being the obvious thing. If your lightsource is occluded it should still cast a light onto the visible area. And if that dragon had a shadow it should show everything and not just the front. But I suppose that's easy enough to implement, just taking the direction of lights into consideration when culling geometry.
The way Cerny mentioned it, he made it sound like the block on the PS5 for this feature was customized and enhanced, which could mean really nice gains if true.
I've also seen that one way this feature can be used is by occluding internal details of a model if pieces of that model itself are not visible. An example would be a high-detail rendering of a desktop computer, or a car engine, with its internals fully modeled, but never rendered/visible due to the hull.
I really, REALLY want to see this tech utulized in a next-gen tech demo of Metal Gear Rising..........................but i feel like this allows geometry in general to be much more robust, and opens up things like better destruction.