| What they are leaving out of the picture, irresponsibly IMO, is that just because a given effect doesn't flip the phase of your signal doesn't mean that you flipping the phase on the parallel blended channel couldn't be beneficial. Our signals are complex, and layering them in parallel increases the complexity, often introducing or increasing peaks or valleys in the wave regardless of the nominal phase. Flipping the phase of ones side is not a cure-all, it does the same thing to your signal but from a different point, so different peaks and valleys come up. The key is to have that tool available for cases where it happens to help. Which, again, has not so much to do with whether a given pedal already flips your phase. | 
