If you exchange hot for ground for both L and R channels, you are reversing the phase by 180 degrees but the two channels will still be in phase with respect to each other. For those who can hear such a phase difference, it makes a difference in their listening pleasure. (One way seems more "right" than the other.) Problem is that no two LPs, and even sometimes no two tracks on a single LP, were recorded with consistent phase. So, if you want the luxury of optimizing for phase, I suggest you research phono preamps, some of the better ones of which have phase switches on their front panels or via remote. You might also do a search on these archives for more info on this subject.
What you did, reversing the phase of one channel, results in one channel being 180 degrees out of phase with the other. This gives exactly the phenomena you describe and is not desirable. One of the Stereophile test CDs demonstrates the effect when the two channels are out of phase with one another. I've heard it, and you described it pretty well. If you like the effect, by all means go for it.
What you did, reversing the phase of one channel, results in one channel being 180 degrees out of phase with the other. This gives exactly the phenomena you describe and is not desirable. One of the Stereophile test CDs demonstrates the effect when the two channels are out of phase with one another. I've heard it, and you described it pretty well. If you like the effect, by all means go for it.