I had a second thought on this and that is - if the cooler mash temperature were not held for the traditional "longer time frame", but rather in the 45 minute range and "incomplete conversion" occurs, will the incomplete conversion allow for the complex sugars to be made from the starches at the higher temperature if the wort is then being heated into the higher range and held there for another 30 minutes? I may just try this out to see what happens....
Isn't this a classic step mash? 145 for 40 minutes, 158 for 30.
Or do you mean the second step is in the kettle? Again, I don't know how many of the unconverted starches carry over. I know a turbid lambic mash uses hot sparge water (200+) to dissolve as much of this starch as possible, since it's desirable for lambic fermentation.