As David explained, it's all psychoacoustics -- giving the listener the impression that the music is higher-energy that it is on the station up the dial. It worked well. I remember how much more exciting the 1967 hits sounded on WRKO than they did on WBZ when I was a 12-year-old listening in suburban Boston, and I was hooked on 'RKO from the minute it flipped to Top 40, even though I'd been a devoted WBZ fan (over WMEX) for a couple of years before then.
Which is exactly what I stated above, we did it in the 90's to make us sound brighter than KYMX and K108 (before). It was never about saving time. It was a setting on the Dennon CD Players. In fact, we had to play the Casey's AC Top 30 in '93 in the production room on Sundays. so that we didn't speed up the pre-loaded commericals on the pre-recorded countdown show on CD. We didn't take that kind of Care in 1995 with Leeza Gibbons...lol
Anyway, it would surprise me if they did it now since the station is truly a Soft AC now.