Leigh, of course - the ramp is a flat surface. That building at the end of the ramp though... the plane of focus will only slice through that building and so technically you can not get the entire building and the ramp in focus on the GG (assuming of course you are focusing wide open.) You also assumed that I meant a flat surface such as a vertical wall. Lot's of examples of flat surfaces, such as the ramp, which of course require the use of Scheimpflug.
Of course I agree that it "does not depend on extremely small apertures," - That works when nearly everything falls on or very near the chosen plane of focus. The moment you have elements that extend beyond the plane of focus you need smaller apertures, varying depending on how far away those elements are from the plane of focus.
I was simply trying to answer the question, which seemed to be one of concept rather than technique. Rick's image shows that he applied the concept of the plane of focus by choosing his subject plane carefully, then used the techniques to achieve the desired plane of focus.