Most games are "mostly static scenes", where the level and lighting stays almost the same. Of course there is a varying amount of dynamic, moving objects but they don't necessarily need to have perfect indirect illumination (that would be hard to spot anyway, since the objects are on the move).

The primary contributor is from the games industry and the results they show were generated in <4ms, so this is probably specifically targeted at games.

There were even some "approximate dynamic occluders", which seem to work alright as long as the occluder isn't too near the camera.