Posted 2022-August-21, 23:46
Much of human defensive logic is along the lines of "would declarer take this line if they held a certain hand"?
GIB doesn't have any such logic. It thinks that it's just as likely as anything else that North started with a singleton diamond, was a total imbecile and forgot to cash his diamond winners, and now has no way to access them in dummy.
It therefore includes lots of hands like this in its simulation, and in these cases a diamond never costs but often gains.
As usual, this doesn't mean it will always throw a diamond in this case; it sometimes throws a heart, sometimes a club, and sometimes a diamond, depending on how many singleton cases it ends up randomly dealing. So playing this way didn't guarantee winning; someone at another table might have gone for the same general line but played slightly different cards, and GIB ran a different simulation and didn't throw a diamond.
But it certainly doesn't harm keeping GIB in the dark about your hand and your options open as long as possible to increase the chance of a mistake.
I have nothing worth contributing, bye