There are some variety hits stations not owned by CBS.
But as to Philly, I don't think Ben is the primary reason, WOGL differs from many other CBS classic hits outlets. CBS is far from afraid of competition. Heck, they're willing to try to take on Q, or at lest swim in the same space. If their research said dumping the '60s and jumping heavier into the '80s would be advantageous, they'd be doing it. They already have some valuable cross promotional platforms that Greater Media lacks, and don't seem averse to spending money (maybe not Jerry Lee money, but still) on marketing. I don't see a reason they'd be afraid to try to use some of that muscle if there were a payoff.
But markets aren't all alike. If the target audience here is more accepting, even welcoming, of the heavier concentration of '60s, then for now it makes sense to, generally, stay the course and transition at a different pace than, say, LA.