You must remember there was no stereo then. It was but only in movies! everyone had mono record players, and AM radio was the thing. One mono speaker. It was not until a few years later stereo became available to us. The old man worked at GE where I live years ago they made radios here, and he brought home a GE stereo, with FM! There was no FM radio then. I can remember going thru the FM dial and nothing came back. This music I first heard in Mono. I loved the shit out of it! Did not know better! So, to say the mono version 'sucks" is a wrong statement, it should be the mono version is not close to the 5.1 version. That was made from mono master.
If you look you will see the absolute inferior recording equipment they had then. So, although I have not had the chance to hear it yet, I will never forget the day my friend played it for me the very 1st time. I was 16 and this music was new! It was different, this was not the Beatles I knew. The very reason I am so passionate over this album.