Pre-exposure, as I understand the concept, allows us to bring more shadow detail up into our printable range without increasing or affecting the rest of our image significantly, the higher values remain essentially pegged, they don't slide up the curve significantly. Pre-exposure allows us to minimize the image exposure to protect highlight separation. The only way I know to get a wider SBR to print straight onto a given grade of paper is by reducing the film's CI somewhere. Pre-exposure as I understand it, reduces the contrast in the shadows/flattens the toe to do this. This is what Dunn & Wakefield and Adams seem to be saying.
Is that understanding of pre-exposure true or false?