3442 is mandatory, but 1♦ opening also shows values in ♦, not just 4 cards. I don't know where did you get that quote, but it has nothing to do with this situation. IMO in this situation penalty double has no merit (and i can assure, that you cannot have 3 trump tricks), so why give away 5 imps? or hope for distant -1 and +3 IMPS, while we have 10 or 11 trick in ♥.