Whether distilled water is more reactive near it's boiling point than tap water is a question for chemists. But, my old english mechanic mentor once told me not to use distilled water in the radiator.
I never have nor have I ever had to replace any cooling system components in any car except my 300E. It was leaking a little around the water pump and then broke it's neck at the top of the radiator, both well known problems with this model.
This level of care is interesting since my new V8's seem to run hotter than other engines I've owned. I'll watch to see what the majority opinion is on "water" Sparkletts or Arrowhead