Yeah, “classic hits” emerged mostly in the early 2000s
The term "classic hits" was adopted by stations that played newer oldies when it became evident that traditional oldies format that were 60's based no longer delivered the 25-54 audiences that agencies looked for. So stations that eliminated, gradually or dramatically, the 60's and early 70's felt they had to put a new label on their approach so they would not be tainted by agency buyer beliefs that "oldies" meant "seniors".
Arbitron had a process for adding a new format name for their service, and it involves a certain number of stations and a certain number of owners and markets that all agree on a suggested new term. I spearheaded the adoption of "Spanish Adult Hits" around 2005 and we got agreement by several other ownership groups and had enough stations in the format to get Arbitron to add a new format name.
Similarly, it took a while for the "Jack" and imitation format to originally be called "Adult Hits"... prior to that many classified themselves as oldies, in fact.
These are just names used mostly for sales.
and became more popular for, at the time, Cox’s River/Eagle stations, WROR/Boston, etc. After the 2005 purge of so many 60s based “oldies” stations that couldn’t evolve properly and went away in so markets, when the former started coming back post-PPM launch the format changed to “classic hits” - essentially The River, but with a focus on late 60s-early 80s pop and rock and it just became the industry term for what was once the oldies format.
The term "classic hits" had nothing to do with the introduction of the PPM which did not broadly occur until 2008/2009. The evolution of "oldies" into "classic hits" had to do with the aging of audiences in diary markets and the need to update stagnant libraries.
Many stations that had identified as "oldies" but which had few 60's songs left in the library just changed their Arbitron designation from one name to another.
And, depending on the market, classic hits stations were more rock or more pop or more of a balanced blend. It all depended on each individual station's market, its competitors and the resulting research target for music and perceptual testing.
Some stations just gradually evolved successfully and went from oldies to classic hits. But yes the original format The River had was what was initially classic hits, an AOR presentation that omitted a lot of “hard” 70s and 80s rock.
Those "oldies" stations with significant audiences... like CBS-FM and KRTH... did research and evolved to catch up or keep up with and under-55 target's preferences and that was all based on finding which specific songs that group´wanted. There was no predisposition to lean towards rock or towards pop or any other style. Each market's research determined the composition of its libraries.
I’ve noticed (Don’t You) Forget About Me on classic rock a lot recently. Perhaps they’re moving in to more new wave?
Or maybe that song crosses over the arbitrary classifications of music types we are engaging in here.