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Thanks for all the responses
I think everyone is saying that 5 hearts and 4 diamonds in the OP sequence is based on inference and elimination. That sounds fine by me.
Each of the four sources in my OP all make terse dogmatic statements, as if the subject had been fully discussed earlier and they were simply repeating the statement.
For example, No Fear Bridge makes the following statement: "This shows 5+ cards in the first suit and 4+ cards in the second suit."
I worked out all the possible combinations that would produce the OP sequence. I agree that, except for some 4441 hands, all sequences will show 5+ hearts and 4+ diamonds.
For 4441, it depends on which rule is used to open (the four sources have three rules). But some legal sequences will be the same as in the OP, which means that some hands will be 4-4 in hearts and diamonds.
However, I think I read somewhere that responder should always assume that opener is 5-4 - even with some ambiguous 4441 hands. They claimed that the assumption would gain more than they lost, because (a) 4441 hands only account for 3% of opening bids, and (b) some of that 3% might clearly NOT be 5-4 because of the sequence and the rule. But even that source didn't mention that the 5-4 is based on negative inferences.
Thanks.
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