Since no two shells are the same, it shouldn't be surprising that many shoes react differently. Any shoe leather reaction to moisture is determined by the type of hide, the tannage, the finish applied (by the tannery), the construction of the shoe, and how the shoe is finished (by the shoemaker) and then cared for by the owner.
I'm assuming that we're talking about the blisters/bumps that some shells develop when they get wet... It happens to some and not to others, it's just the way it is! The answer is always to brush, and if this doesn't fix it, then rewet them evenly and allow them to dry naturally. Then, brush.