I am not surprised, as most things that generate light are generating photons using quantum effects, and thus are true random. Furthermore, CCD and CMOS detectors themselves have a quantum efficiency less than 100%, meaning they only detect a fraction of the incoming photons at random. So, a regular light bulb in front of a webcam is already a quite high-bandwidth source of true random numbers.
So, there is nothing revolutionary going on there, this paper is more about how to build a system with micro-LEDs and a photodetector and how to remove any inherent biases in that system, with the obvious benefit of being able to make something very compact.