you use illegal methods to get X without a warrant. but you can't use that information legally. so you use your knowledge of X to find a legal way of learning X, after the fact.
then you go to the courts saying you found X the legal way.
I understand the theory thanks, I'm just disputing that this scenario is anything other than exceptionally rare. Parallel construction is used to protect sensitive sources, not cover up illegality.
you use illegal methods to get X without a warrant. but you can't use that information legally. so you use your knowledge of X to find a legal way of learning X, after the fact.
then you go to the courts saying you found X the legal way.
but you didn't.