You started in the wrong thread! We discuss these things as well as others in this thread
https://www.homebrewtalk.com/f12/westvleteren-12-group-brew-swap-121429/
Short answer: Brew Like A Monk states directly from Brother Joris, head brewer at Westvleteren, they only use pale 2row and pilsner malt and sugar to achieve their magnificent flavor. The many times I have brewed the "Traditional" recipe it has come more or less exactly in line with the real thing. That being said the "New World" recipe is also nearly indistinguishable from the real thing too. It is replicating what the monks do with decoctions with specialty grain. Even though my New World recipe won this competition I personally prefer the Traditional recipe.
Also, the late additions of sugar are to keep some of the volatile flavors that the dark sugar has. I prefer to put it all in the boil kettle so that it dissolves completely. I tried it in the fermenter one time and found some unconverted in the trub. I don't think the Westmalle yeast needs help drying out if you get the temps properly.