Suppose that the bidding has followed a simple route: Two No-trumps by South, raised to game by North. West makes his normal lead of the five of hearts against Three No-Trumps which then goes to the two, queen and ace.
Clearly the diamonds have to be brought in and the percentage play to handle the suit is to cash the ace first, planning to finesse the jack on the second round. This does cater, of course, for the possibility of East holding the singleton queen.
There is, however, the very real danger that, if the finesse loses, the defenders may find the damaging spade switch. Indeed, what happens if declarer adopts this line? On the second diamond, West discards the nine of hearts, warning his partner against continuing hearts and directing his partner to the highest-ranking suit, spades.
As Granovetter points out, a far better practical bet is to finesse the jack of diamonds at trick two without cashing the ace first. If this loses to East, his partner will have had no opportunity to signal and, as a result, it will be far more difficult for him to find the killing spade switch.
You may not approve of everything that the author puts forward, but you do have to admit that his ideas have the merit of freshness.