Is the meaning that impurity does not transfer after it has completely dried, or does it transfer if water comes into contact with the dry impurity and then touches a dry, pure object, rendering it impure?

The intended meaning of "transferred impurity" is any impurity that has wetness, whether the wetness is from the impurity itself, like urine, or if the impurity was dry and then mixed with water, or if it was dry and something wet touched it, thus transferring the impurity to it. Some scholars differentiate between "rutubah" (dampness) and "balal" (wetness).