Well, remember, you don't have full information. Especially in an "all pass" auction from opponents.

Interestingly, the computers would to MUCH better on defense. Because as you bid, you speak about the distribution of your hand, and your partner does the same about theirs. (Even in negative inferences.)

And trust me: Good opponents will use that information, already.

So far, bridge has found the smoking guns because honestly: The cheaters have sucked at cheating.

If they bothered to actually encrypt their signals at all, they would have been suspected, but not caught.

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To answer the question: Even today. Good players will know the answer to when to take which finesses. Where good, is probably around Life Master and a bit under.