Section 9 of Etiquette provides: "If a player say, 'I have the rest,' or any words indicating the remaining tricks are his and one or both of the other players expose his or their cards or request him to play out the hand, he should not allow any information, so obtained, to influence his play, nor take any finesse not announced by him at the time of making such claim, unless it had been previously proven to be a winner."
The case under consideration is covered by the first portion of Law 72. The latter portion of that law does not apply, as the opponent did not place his cards on the table after a claim by the Declarer.
The law seems clear, the cards of the adversary are exposed and subject to call—the cards of the Declarer cannot be called.
The etiquette of the game, however, must not be disregarded.
The plain intent of Section 9 and the justice of the case is that, if the Declarer place his hand on the table claiming the remaining tricks, he should not receive a doubtful trick unless, when he made his claim, he contemplated any finesse necessary to obtain it.
If he did not intend to finesse that way, or did not then realize that a finesse would be necessary, he should, under these circumstances, voluntarily surrender the trick.
The reason for this is that, should a Declarer claim all the tricks, the opponent who requires the hand to be played out would naturally hold the strength; the locus of the request, therefore, suggests the way to win the finesse.
It is most advantageous for the interest of Auction that, when no real play remains, time should not be wasted, but neither side should in any way benefit by an effort to avoid useless delay.
In the case under consideration, however, the adversary suggests that the hands be placed on the table, and the Declarer may naturally expect that the only card which might take a trick will drop.
There is no reason to assume that the Declarer will not finesse correctly, and it is not just that the act of his opponent should deprive him of the opportunity of so doing.