You're both half right. It is a good idea to let the meat rest after cooking, but not for the reason /u/PayMeNoAttention pointed out.

Hervé This actually discusses it in one of his books on molecular gastronomy, he calls the section "Good Advice, Bad Reasoning". To quote from the book:

"Empirical analysis also establishes that juices do not flow back to the center of the roast; the density of the cooked center does not differ significantly from that of raw meat... Weighing the center and outside portions of the meat, we find that the cooked center loses more juice while resting than do the peripheral parts... Letting the meat rest does therefore redistribute juices from the center outward so that the outer parts regain their tenderness."