[Strawbale] Bottom of wall detailing

[N Leone]

Hello again. 

Another question about a detail from Bruce King and Crew's Design of Strawbale Structures.  (Anyone get the impression that 1) I just finished reading that book, and 2) I'm in the "details" phase of my house design?)  On page 216, illustration 10D illustrates things to keep in mind when detailing the bottom of the wall, specifically in the "no earthquakes" areas.  The graphic shows the top outside corner of the grade beam notched down below the sill plate with the exterior plaster running down to that point as well.  The note referencing that area says "The outer plaster should sit on a shelf in the edge of the foundation below the sill plates..."  So my question is:  Why?  I know adding that notch to a poured grade beam might not be too hard, but it's going to be a bit of a mess on a block stemwall such as mine.  So I'd like to understand the reasoning behind it a little better to either 1) find an easier way to accomplish the same thing, or 2) be able to explain it to whatever poor sap (probably me...) has to make it happen in the block...

Thanks,
Nick