It is not so much that the honey reacts with the bread, as that the concentrated sugars absorb the water more forcibly than the starch in the bread does, so the starch soon is left with as little water as if it had been drying in air for a few days. Not surprisingly it shrinks and hardens in much the same way as it would if it had simply dried out. Notice that the behaviour of the water that vanishes into the honey is in a sense, that it dissolves in the honey.

Think it over.