I have had numerous books pressed before grading by CCS, and only once was I a bit confused when i sent in 3 copies of a particular issue and 2 came back 9.8 and the other a 9.4, with notes saying stress to spine, I thought this odd as i believed a press should eliminate stress lines that are not coluor breaking, but on a whole 2 out of 3 is a good average, and I have had more successes with pressing, in a lot of cases bumping up a grade, so even with some questions in regards to grades i may think i should have got, my overall experience with CCS, has been pretty good and i continue to use them.
Maybe some who grade their books, may need more experience in how to do this more acurately, a lot of us think we should get certain grades, but a press will not always eliminate all defects.