(shrug) Indeed. More generally, he's a bounded agent, there's always a thing-to-be-told, which may or may not have anything to do with solving jigsaw puzzles.

For example, "there's a piece that fits with another piece somewhere in this puzzle box" is certainly a thing to be told, and is always true of non-pathological jigsaw puzzles. And "There are no sharks on Mars" is also a thing his brother could have told him.

But, yes, if the Shannons didn't have an implicit shared context that strongly suggested that there was a less generic thing-to-be-told in his brother's mind than those examples, then most of what I said about the Shannon example is simply false.