It was, and there are even some significant differences. On she's leaving home, the mono mix was speed up with the mono version's length coming in at 3:26 and the stereo at 3:35 [0]. I believe (running off of memory here too) that the first album where the stereo mix got some actual attention was the white album.
[0] https://en.wikipedia.org/wiki/She%27s_Leaving_Home