The term “dissimilar construction materials” may be the most over-used term in our standards, and yet, it has no definition. This leaves the term open to all sorts of ridiculous interpretations. For example, technically, galvanized and PVC accessories and all lath are dissimilar construction materials; as are sealants and paint. This is clearly not what was meant or intended to be meant by those who authored these standards to begin with.
Adding flashing as a definition is simply to point out that some flashings are intended as drainage components for moisture and should not be sealed. Not all flashing diverts to the exterior. Some flashings divert or direct moisture between the 2 layers of WRB.