It wasn't intended for a communications relay, but it was intended to have 2-way communication. I went down a rabbit hole reading ArXiv papers about it. Despite their tiny size, the probes could phone home with a smaller laser - according to the papers I read, spinning the photons a certain way would differentiate them from other photons, and we apparently have the equipment to detect and pick up those photons. The point of the communication would be for them to send back data and close-up images of the Alpha C system. Likewise, they could receive commands from earth by having dozens of probes effectively act as an interferometry array.