There is a difference between puddles caused by uneven grade of the pavement and flooding. Puddles yes at MK, flooding no.
All four parks were built on swampland. A large amount of dredging was required to raise the parks above grade. Fort Wilderness floods because it preexisted the parks on Bay Lake. The parks get puddles and the surrounding area can flood into the drainage systems but the parks themselves with a few exceptions (AK comes to mind) will not flood to a point that they can not be quickly cleared.