Cleaning virgin ADG, Peterson, Lapua, Alpha, isn't "required" per se. Higher quality brands come very clean.
Just food for thought...
Some high quality brass even comes in ammo boxes to prevent shipping damage, but I have yet to see a production line where necks have 100% protection before they are placed into those containers. I have still received high-end brass in boxes with dented necks and they still need to be chamfered for most applications.
If your new brass is out of round or dented, you shouldn't chamfer it before you round it. If virgin necks are dented or out of round, a chamfer tool will create an uneven cut. That neck will then be forced into rounding by your bullet, but at the risk of friction variations or even scratches on the jacket.
You can alternatively flare and taper crimp to avoid chamfering virgin brass like many factory production lines, but that is a whole other detailed discussion.
When you run an un-lubricated/non-treated mandrel into a virgin unlubricated neck, you run the risks of galling, so many folks will "wet" lubricate before chamfer or neck sizing. That results in a reason for post prep cleaning. Some folks do it unlubricated with success, and others get burned by galling. You have to decide for yourself.
You can however, get away with mandrel sizing with one of several dry lube methods which makes post-prep cleaning optional again.
So, the short answer is like DMagna says, but those other issues are worth mentioning in case you haven't thought about them before. YMMV
