I assume this was meant to be a generalization, but I have to disagree with your core argument here. The "upgrade" is the point of pressing...unless the owner presses purely for aesthetics and keeps the book raw. Of course there is no guarantee of an "upgrade", but pressing absolutely has bearing on the likelihood of the bump.
It's very true that pressing can introduce defects, but that's a very small minority when considering the total number of books pressed on the daily. Aside from my first submission before pressing was a thing (and 3 moderns I sent to another company), every one of my self-submitted books are CPR'd. In every case to date, the books came back higher than my assigned grade or the previously assigned CGC grades in the case of crack, press and re-sub books. My experiences may be an anomaly, but it's a consistent one if it is.