The stereo remasters are completely different mixes of the Beatles work made to be listened to in stereo. They didn't take the mono tapes and remaster them in stereo... each version was done separately and up until the White Album, the mono mix was handled first and given the most care. When listening to the stereo and mono mixes you can hear things on the mono version that were left off of stereo. Folding that down to mono will lose even more.