Some of your points are lacking a little bit of basic understanding. Comparing a HOF rookie card's percentage of qualifiers to the nickel commons in the same set with qualifiers is a fool's errand. No one submits off-centered 1980 Topps commons to any grading company. However, a bunch of people submit off-centered Henderson rookies in the off-chance they get PSA 8s and have some value graded.
Same for print defects. People will send in valuable cards with print defects, but not commons. You seem to hand-wave at that, but these cards are not needed to make your point.
Using the '52 Mantle in your comparisons is also a bad selection. Unopened packs of 1980 Topps are still very common, while there is no true access to unopened 1952 Topps High Numbers anymore. So IMO there is no utility to the 9s vs. 10s ratio between these two cards. Jeter is a much better example.
I would agree with your premise that many of the 9s could/should be 10s, and that PSA is likely to be keeping them close hold like Bitcoins being mined at a slow rate to increase their after-market value.
BTW, did you happen to see that many of the PSA 10 Henderson's have been removed (temporarily?) from the Pop Report?
https://www.blowoutforums.com/showth...derson&page=44