he's saying that the return pump could fail after the power comes back on and the water in the tank will get cold because the heaters are in the sump, and you are away from the tank long enough for something bad to happen.
But if the power is back on, won't the house heating (and tank lighting, powerheads, etc) be back on as well, minimizing the temperature swing?
Too many ifs in this discussion, and yes power cords really do look that bad.
jp