Foils are often under graded by their owners because of surface issues. In addition to other issues, foils have the additional chance of having surface damage because of oxidization on the metal
PSA does take off points for printer dots. Sent in a card I thought was a Ten and it scored an 8. Everything including surface was flawless under magnification. After the return I found a 10 on eBay and did a comparison. My PSA 8 had a couple printer errors, the PSA 10 on eBay did not.
Hey there, came across your channel and enjoyed your magic reveal. I have done one submission of magic cards so far (my video for it is up on my channel) and had similar results. I feel like whoever is doing MTG grading at PSA is much tougher with grading than the sports card graders (of whom I also do a number of submissions for), especially with foils.....especially with foils. It makes me not want to send in anymore magic cards to PSA. I think I may do some crack outs on some of my magic cards that I sent in that submission, but I am concerned that they have fewer graders doing magic, and I'll end up sending them to the same guy who graded them the first time around.
Thanks for checking out my channel! Yeah unless the TCG card is flawless and you think it’s absolutely a 10, I would send it to BGS (or send it to BGS anyways to attempt a black label). BGS is really harsh on centering but pretty forgiving on the other subgrades in my experience. Good luck with your submissions!