Couldn't agree more - it is just experiences shared in common by several BC'ers, some of whom are really outstanding bass players.
Just to go back to my OP, when I switched from P to J pup mid set for a song with a lot of low B work with exactly the same EQ settings, our drummer, who has a really excellent ear, did a double take and said "whatever you just did - keep doing!" He could hear me cutting through the mix with that one change. The P and J pups were set up just fine for the rest of the set on songs with less focus on the low end.
As I hope I've made clear, plenty of folk won't have experienced this issue on their set ups. It's just a little 'gem' that may come in useful to some of our fellow musos along the way.