Simple answer is that you don't always know when it is a Streamlined "k" or a Full. We had a glazier buying a home... he felt that he could repair the broken windows so they had the contractor bid on the roof, carpeting, & new kitchen leaving off the broken windows. The appraiser called the broken windows tripping this into a Full 203k requiring a consultant. Had they merely mentioned this ahead of time this would have been a Streamlined "k".
Another one we just saw appeared to have structural issues in and about the garage but turned out that we were removing the garage which then removed the structural issue & left it a Streamlined "k". Had they wanted to repair the garage it was a Full 203k.
Having your consultant do the inspection on the property can let you know sooner that is one or the other, & in some cases save it as a Streamlined "k"