The stereo reverb effect I'm thinking about doesn't require input that's different on the two sides, like ping pong delays. If you clap your hands in a cave, that's more or less a single point source, but the refections that come back are most definitely stereo, giving a sense of the dimensions of the room.
Most reverbs that are stereo out at all do this, generate stereo output from a mono source. Some also try to generate realistic stereo output from stereo sources. The block diagram earlier makes it clear the the Axe doesn't do that, it sums the inputs to mono. It's unclear from that whether the generated reverb reflections and tails are are stereo, but I strongly suspect they are.
