Posted 2015-September-14, 18:17
Strangely, I suspect that the core misunderstanding may be earlier in the auction. The trouble bid might be 1S.
The style is a weak notrump opening. Typically, then, Opener doesn't bid 1S with the balanced 15. Instead, 1NT to put the points on the table. 1S, then, already shows an unbalanced hand. If so, then at the 3C call, Opener has extras, because 2D, or perhaps 2NT, would show 4153 type, minimum.
If West thinks 1S just showed spades, and might be balanced, then 3C was "needed" to complete pattern. West missed that this is redundant, and hence missed the inference.
If, inztead, the style is as West necessarily must have assumed, then the partnership needs a more artificial unwind after 2C. Typically, 2D minimum and non-committal as to shape. But, even that would make 3C extrss.
The only scheme where 3C shows no extras is an insane requirement for 2D showing length in diamonds immediately at the cost of an intelligent way to handle the very likely this pattern, in which case the agreement is dumb.
If there is no agreement, get one.
"Gibberish in, gibberish out. A trial judge, three sets of lawyers, and now three appellate judges cannot agree on what this law means. And we ask police officers, prosecutors, defense lawyers, and citizens to enforce or abide by it? The legislature continues to write unreadable statutes. Gibberish should not be enforced as law."
-P.J. Painter.