I'm not at my M8 machine but I'm pretty sure that clicking on a top 'layer set' tab
doesn't change the bottom 'layer set' tab even without the crossfader enabled? - If I understand you right.
This effectively gives you 16 'layer sets' of 5 layers to play around with.
This can be really useful for involved gigs, 5 layers goes a long way, and it can also give
some great 'fading' effects when you change sets ...
especially if you have a bit of trace in the mix.