WEBN's formula of new song/old song/recent song/old song/new song has been around for years. What's changed is that the list of older songs got a little longer.
Years ago, WEBN stopped playing certain old songs and artists (Boston, Tull, Seger, etc.) so that their sister station The Fox could have "exclusivity" on them. But in the past year I hear two things: The Fox has been rocking softer, and WEBN has slowly been bringing back many of those songs.
So, the percentage of old to new on WEBN hasn't changed, but the depth of the older song list has increased. And that started happening long before these recent changes on other stations.