i've never delt with dual mass FW's before so I can't say whether they should or shouldn't be machined. I do know that organic discs need a nice flat surface to bed into. the heat will warp surface and make it uneven giving the disc less area to grab and eventually it'll start to slip. if you where running a copper disc with a really stiff PP I don't think it would matter as much.
I wouldn't install an OEM PP, which doesn't have a lot of clamping force, and organic disc without having them machined. its just asking for trouble down the road IMO.
I thought I had pics of my PP but I don't for some reason... I took pics of everything else though. the first time I did the clutch in the z06 the FW looked like this:
discs where in great shape and the car shifted fine and all for a little while, then a couple thousand miles later the clutch was slipping. This is a dual disc clutch capable of holding 700wtq.
after everything was machined down a few .000 it looked brand new again and has been trouble free.
