The ride height issue you describe is because people have either fitted Elite springs to non Elite cars or replaced the self levelling shocks with standard ones and not changed the springs to match.
In my experience, it is the other way round - Elite springs are softer than non self levelling, so when owners fit the 'one spring fits all' spring to an Elite with the self levelling shockers, as the spring is likely to be firmer, the ride height is adversely affected - usually with the 'jacked up' appearance. Not all aftermarket springs have the progressive would coils with the thin pigtails either which will affect the ride height.
My personal preference is genuine GM rear springs with the correct ident lettering for the particular model to ensure the correct ride height.
Others obviously have their preferences, or don't mind chancing not keeping the original ride height / appearance.