The issue is real, it's the mechanism that's at issue. Clutch is weak, more power shows that if you use it when shifting and accelerates the issue. Clutch doesn't slip at low RPM and high gear until it's worn away from other situations. Once you experience slip you can milk it along for a while but it's time for a swap. George is only protecting you from yourself. If you used your right foot within the same parameters his clutch tune allows at lower rpm, you'd get the exact same wear and no in gear slip until it's about time to replace anyway.
George will also tell you that the JB4 is smoother which you dismissed. I am not saying that you did anything wrong and am genuinely happy for you. I just don't understand rationalizing the JB1 as better for anyone outside of price and simplicity which is, of course, always valid.