If you look at the title and copyright pages of the Volume 3 in the 'Combined Volumes' release of SDM, you would see that it states revision 56, September 2015, even for combined releases 57 and 58. More, it seems that the volume 3 in the combined pdf takes 1942 pages, while stand-alone volume 3 is 1964 pages.
OTOH, looking at the documentation changes document and comparing with the actual content, it seems that the pdf was updated. E.g., 6.15 'interrupt 13 general protection fault' section does mention the CR4.UMIP case.
So it seems that the problem is only with mis-editing the title page for the Volume 3, but the different number of pages in pdfs is still puzzing. Could, please, somebody from Intel confirm that ?