As I have pointed out, 1969 was the year that records mostly stopped having dedicated mono mixes. Late ’68? The Beatles White Album had a mono mix. Fall of ’69? No mono mix for Abbey Road.
The move from mono to stereo must have been on the minds of consumers to rate a comment in this scene from Cactus Flower. Look at all of the Beatles records on display, and there were 8-track tapes a’plenty.