That reason makes sense, and there are certainly rules in tournaments against early draws, but I'd never heard of a rule against resigning early. My understanding of Magnus playing one move was that you couldn't resign until the game started, so he just started the game and resigned immediately, but maybe that's mistaken.
I guess it hasn't come up much since the personal loss of losing a game is usually pretty great at a high level. Maybe we'll see such rules after Magnus' resignation.
