2♠ was intended to show hearts and clubs (the meaning it would have had if North had passed), but EW had not discussed this situation. When asked before South's final pass, West said it showed hearts and an unspecified minor. He had intended 3♣ as "pass or correct".
EW are a long-established strong partnership. They play a version of Ghestem that uses a direct cue-bid, 2NT and 3♣ over one-of-a-suit opening suit bids to show different two-suited hands. In situations where a jump to 3♣ is not available their agreements are similar to Michaels, e.g. (1♥) - pass - (2♥) - 3♥ would show spades and a minor.
West reasoned that this was one such situation as East might need 3♣ to show a weak hand with long clubs (a sort of "post-empt"?) Their 2♣ opener is Precision-style, and their 3♣ opener shows an opening hand.
Result: 3♣X(W)+1, NS-570
South claims that if he had known that 2♠ showed hearts and clubs specifically he would have bid 3NT (which he admits is unlikely to make).
Does South have a case?