I haven't been able to find anything but it would be good to know exactly what is going on, I'm curious. The answers might be in here. Kai, I don't suppose you have this book?
This book has some info, but not as much as you can find in Kunze, Briggs or Narziss/Back's other book (Technologie der Wuerzebereitung).
One important aspect, that we brewers tend to forget, is that a-amylase is also active when the b-amylase is active. So once the starch gelatenizes and there are lots of starch chains to break a-amylase will randomly clip them and provide more substrate (chain ends) to b-amylase.
In the most idealized form the amount of fermentable sugars produced depends on the "time" that b-amylase is active. When I say "time" I actually mean the area (integral) under the time-activity curve. This time can be controlled by temperature, which we do in single infusion mashing, or by the length of the maltose rest, which is done in the Hochkurz mash. Again, this is very much idealized.
If you want to have highly fermentable wort you need to keep b-amylase and possibly also the limit dextrinase active as long as possible while giving it enough dextrins to work on. In brewing this means you need to mash at a low temperature but high enough get the starches gelatenized.
One way around this is to do a decoction mash or like a decoction mash. Pull the liquid out of the mash, raise the temp to 160-170 F and let the mash convert, Then return this back to the liquid to reach a temp of 60F. Now the b-amylase and limit dextrinase have lots of dextrins to work on and they'll survive much longer at this lower temp. A rest temp that would not have been practical with normal mashing since at this tempt the starch hasn't gelatenized yet. But this is only a technique for ultra fermentable wort.