RoboTech,
I can tell you, because I've used it in labs, that Distilled and deionized are not the same, and that the statement does not apply to either types.
The distilled water can be produced in many ways, but the simplest, and the defined way, is that the water is boiled, and re-collected as it condenses against a cold plate. The process removes biological things, but leaves some salts.
De-ionized water is completely stripped of all ions, and contains nothing but water. As such, it's in an unstable state, and it will regain it's balance, by stripping off ions, as Alchemy described above.