Borrowing ideas from the maker movement and agile processes, we see this a way of doing rapid prototyping for training. We take the emphasis off theorising and analysing, and shift it to practice and trying things out. When a group gets its pace, it gets to experiment with lots of different approaches, and can use both conscious and less-conscious ways to evaluate what works. And unlike so much training, we aren't wasting valuable group time for a top down content dump.
There is plenty of content out there for every subject under the sun... but I think it's a terrible waste of group time to plod through a book or manual. If participants like the book, let them read it at their own pace. If they don't like it, then why make them pretend to engage with it at all. I would quite like to ban the whole "turn to page 94 of your manual" schtick and the fetishisation of binders of processes. Especially for the complex, intractable problems which most concern people.