Spielstich

Slam bidding. Because 3♥ would risk otherwise to miss the last halt to 3NT if opener holds no ♣stop like here. The other possibilitiy would be that the responder bids with ♠Axxxx ♥Kxxx ♦x ♣QJx 3♥instead of 3NT in the hope P has 3♠ or 4♥ and finally corrects it to 4NT - what no P can understand. As ♦ bidder I would not assume that P misbids and assume RCKB.