You're right. History: the gauges of this set are modelled after the original Fender flats of the late 50's and 60's. The G is greater diameter to keep it from sounding thin and increase sustain. The E string is made thin so it will vibrate in its overtones easier for consistent tone and not go thumpy. Yes, this is a modern tone set with growl. That is the way it was designed. Yes, they work great on a J-Bass, especially the 9050L set, 45-60-80-100. They discontinued my favorite set some years ago, the CL, with 45-60-80-105, which addressed your criticisms on tension and feel, which were also my criticisms of other flats sets of all makes. I have scrounged one set of NOS CL's and have another used set on the way which should last me quite awhile. For your P-bass, maybe a set of La Bella 760FL 43-104 would suit your preferences?