Great question. The idea that the two move towards equilibrium and pass one another, for no specific reason, doesn’t make sense. The idea that crackers are saltier could be very important, because including salt in a recipe will make the end result equilibrate with the atmosphere in a wetter state, other things being equal.
Three more possible explanations:
Bread feels more dried out, and crackers feel more soggy, because we are used to their normal states, which are soft and crackling dry, respectively. So, if you carefully analyzed the end results you wouldn’t still think the cracker was wetter and the bread was drier. But, I don’t like this one much - surely we are aware enough to see past this one.
And, bread is leavened, whereas crackers aren’t. Bread has some kind of toughness as a result, and winds up stronger in the dried state than crackers do. This is similar to how crackers are easier to crumble into crums than bread is. I’m not sure this is true, but the leavening is certainly a difference. Melba toast might be another good test case, if it is chemically closer to bread but physically configured more like a cracker.
Finally, all wheat flour is not the same. I heard something recently about how different some pasta flours are from bread flours, which are different from cake flours. There aren’t that many kinds for sale in the grocery store, but a mass producer of crackers or bread could have all kinds of reasons to choose a particular and distinctive flour.