SCTs and chromatic error on double stars

Hi, Roland's point that an SCTs spherical mirror induces chromatic error or
imbalance leads to some questions. Is that also true in Mak/Cassegrains?
Why doesn't the corrector plate "correct" for this in an SCT. In about 5
years I'll be looking to buy that "retirement scope" in the mountains in
south eastern Colorado. Is a D&G 20" classical cassegrain a good choice vs.
a 20" Starmaster for DSOs? Thanks to all in advance ...