This hand occurred in the first of seven swiss matches at a Regional yesterday. My partner and I did not bid the heart slam. At the other table, there was no 3♣ bid, and the opponents did bid the slam, but the way they bid it made no sense to me. My hand (responder) bid Jacoby 2NT, and over opener's 3♣ shortness showing bid, signed off in 4♥. Opener then drove to slam.
Note that if opener is 2-1 in the minors instead of 3-0, slam is unmakable on a diamond lead assuming that clubs are 7-1 (unless the hand with the singleton club has no hearts or only a singleton ♥A).
Your thoughts?

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(P) - 1♥ - (3♣) - ?