After the Opener rebids his diamond, the Responder realizes this is a heavily distributed hand. The Opener may suspect, but does not know this. Not wanting to do the bidding war between a 6 card diamond suit and a 6 card club suit, the responder suggests looking for a 3rd suit or no trump. With no hearts to bid, and not having a stopper in hearts, he bids his 4-card spade suit. Now all the Opener knows is his partner did not support his diamonds (he has 1 or none). His partner is looking for something besides the minors to play and skipped over bidding hearts. This partner, using the information available, decided to play 4 spades (maybe he does not like playing no trump, who knows?) Would it be wrong for him to bid 3NT? Of course not … as long as he did so using all the information available.
14 June Facebook hand: