Limits of MF pads on the finer end

I feel confident I understand the use of MF pads on the aggressive end of the compounding scale. And although I've read that foam is still best for finish polishing or jeweling, something I keep seeing makes me wonder if they will continue. I keep seeing where MF finishes out better with the compound end of the scale than foam - SO why wouldn't it finish out better than foam on the low end of the scale? What's the mechanism at work in this or has it just not been experimented with enough? Hopefully not too silly a question but just something I keep wondering.