The way to do the math on these is to realize that 35+ means 35 to literally however old the oldest listener in the market is.
When you had a station billed as a "35+ format" and you could not find them performing well even in the 35-64 demographic, that meant the 35+ was really 65+, and after the early 1990s, that was the story for these---hence KFRC flipping to oldies, KMPC to sports and WQEW (the re-born WNEW) to Radio Disney.
An 80-year-old now was born in 1940---making them 16 when the first wave of rock and roll (Elvis, Chuck Berry, Little Richard) hit. Which is why oldies is no longer a viable commercial radio format, either. And at 80, they're too young for Standards in any significant numbers.