"Taking advantage of fungal mycelia’s natural light sensitivity, Mishra et al. developed an electrical interface to both house the mycelia and measure their electrophysiological action potentials. A control model was then developed to use the rhythmic voltage spikes from the living mycelia to control the locomotion of both a soft starfish-inspired robot and a wheeled robot. Robot trajectories could be altered by stimulating the mycelia with ultraviolet light. "

So. The mushroom was used as an ultraviolet light sensor, not just an RNG. But you could imagine it reacting to anything that might interest a mushroom. Food? Some sensors could be more useful than others.