[djaychela]

I think it's referring to the interference between devices that happens when they are communicating via radio at the same frequency - light doesn't interact in the same way so you can have much more information transfer happening in a space and not have those light channels interfering with each other. Clearly, though the other points you put about things interrupting the light and therefore the data is an issue, but I'd imagine that the protocol has ways of mitigating that (as, I believe, networks do anyway, where a packet needs to be acknowledged or can be requested to be re-sent?)