20-minute mash time for Stone clone?

I'm looking at the Stone Pale Ale clone from "The Craft of Stone Brewing Co." and their mash schedule calls for 20 minutes at 156 degrees F. I always thought that at least 30 minutes was required for conversion, with one hour being the safe bet. 20 minutes seems short to me. Has anyone brewed this beer, or worked with such a short mash time? The recipe also recommends following that 20 minutes with a 165-degree mash out. Here's the grain bill:

10 lbs 7 oz two-row pale
1 lb 4.2 oz 60L
4.8 oz 75L

North American 2-row is so high in diastatic power that it converts low adjunct grists in no time at all. I had a mash that tested negative with an iodine test after only 15 minutes.

Just a shot in the dark here, but they also brew on a much larger scale with a much different system than most homebrewers. I would cut the caramel 60 some... see last page.

http://www.stonebrew.com/news/081201/