> Cloth nappies seem to accelerate potty training too (we've done cloth and compostable, solely the latter with current child), I think they can feel they wet themselves more easily, better feedback. If the nappy is so "good" they don't feel wet then there's no intrinsic incentive and no feedback.

Modern diapers are so good that they're counter productive to potty training. The innards whick all the moisture so the child's bottom remains completely dry until it gets extremely saturated.