Recently found this 1987 interview with George Martin by Allan Kozinn, wherein the Beatles producer tackles the mono vs. stereo debate and explains why he remixed Help! and Rubber Soul for CD.
GEORGE MARTIN: Yes, we were still doing different things then, but I was still working towards the compatibility, and in fact my attempts on “Rubber Soul” were to find a decent mono result from a stereo record. As you know, if you put something in the center, it comes up four dB louder in mono than it does in stereo. But if you tend to balance your things between one side and the other….And also, I was aware in those days that the majority of record players in the home were built into kind of sideboards, where the speakers were about three feet apart, and the stereo picture was a very near mono one anyway. So I exaggerated the stereo to get a clearer effect. These were experiments. It wasn’t a question of rushing, I really was trying all sorts of things.
The whole thing is fascinating, and it’s crazy to see how cavalier Martin is regarding the historical importance of the original mixes, and how utterly uninterested he is in the mono mixes of the later (65-68) albums.