Oh I see, you say using AHR for direct also? You can do something like that with emissive objects, using them as area lamps, they cast correct contact hardening shadows and the performance is independent of the number of them. Still, the range is limited and the shadows look blocky, but working on improving that. I have played with using AHR for just shadows before, and while it works, it has too many limitations. Think that after it’s more mature, emissive objects could be used to handle some lights.
In any case, is mainly for the shadows, as deferred lighting is extremely efficient for many lights.
Think we’ll see after gets some more work.
EDIT: The difference between using emissive objects and the link you posted, is that he computes shadows per light, so the more lights the more expensive it is, with the emissive objects they just “get” in the way of the GI tracing, so you get the shadows + lighting there, without an impact on the number of them