I’m interested in hearing what you observe when you get the cards back in your possession. I have a hunch (completely devoid of any evidence whatsoever) that PSA unintentionally damages condition-sensitive parts of cards with how they’re handled between the different steps of their grading process. I, like you, very carefully observe cards I submit and avoid submitting holos with random light scratching (not print lines), which is almost guaranteed a 7. Yet, I’ve sometimes received cards back that have ended up with random scratching on the holo–sometimes the grade reflects the random scratching, but sometimes not, which makes me think that there are steps before and after grading where this scratching may occur due to how the cards are handled/stored.