Or, more likely, the did cluster/factor analysis and found that there was a bigger core with a rock leaning version of classic hits than with a pop/CHR leaning version.But the testing on that music (as you know) isn't based on response when the songs were popular, but how listeners react now. So perhaps musical taste changes as people get older. So people who might have been fans of Whitney or Michael in the 80s are less interested now.
What is coming out of this discussion is that they have done more than change rotations... the core "sound" of the station is more Guns n Roses and less Pet Shop Boys and Cyndi Lauper.