Is this theory or actual?
I would describe it as conceptual
. Though it is well done, it is an over-simplification of both the PLC and any possible RF implementations.
In the PLC world, a more accurate representation would have to be more one-dimensional. Like having the signal propagate down pipes from one node to the next, with a star network connection at the breaker-panel. Though that might be more accurate, I don't think it would get the idea across any better than what was presented.
But it is clearly over-simplified for an RF implementation, as it ignores the effects of phase. Though the first transmission would still be correct, the second, third and fourth transmissions would have progressively weaker signals received at the nodes, as "destructive-reinforcement" causes the resultant signal to approach zero as more nodes participate in the transmission. In contrast to the PLC situation, the demo does not correctly show what would happen in an RF implementation.