It probably has less to due with deception, and more to do with ignorance, but many sellers paint right over the top of the rot. Anytime there is an older house on the market, if the home inspector has experience in the field, he or she will be on the lookout for fresh exterior paint that is in place to hide problems under the paint.
I have written articles on this topic before, but the photo below is a wonderful example of someone having painted right over the top of the rot at a rafter tail. The problem area is the wood at the left end of the gutter.
If the person who did the roof had put a shingle or a flashing over the rafter tail, so rain water coming off the sloped roof would have been routed over and past the wood tail, this might not have ever been a problem. In this case, and oh so common, the rain coming off the roof soaks into the wood and rot prevails. That is the simple science of rot and very important to remember, when building so the structure will last, in the wet environs of Bellingham and Whatcom County.