Rick--yes, over winter was kind of a figure of speech and technically, to broad. The increase bulk must be in response to the very slow and gradual warming of the soil and in preparation to shoot up the stem. Probably as early as late February or as soon as the bulb senses the soil is warming. I think your post describes it very well. Bulbs must have to do this (rehydrate) naturally in order to support stem growth with foliage a foot high or more before it develops functional stem roots to feed the system. It's interesting how bulbs prepare themselves to over-winter and how they prepare themselves again for Spring and new growth.
On quite a few occasions, I've planted Vernalized bulbs in the Spring and then decided to move them to a different spot three or four weeks later. The size and weight difference from rehydration is amazing!
