This looks like what the CGC guide describes as "ink missing" but someone who's expert in ink defects would need to confirm with it in hand. If the area is glossy, then it would likely be missing ink. If it's duller than the surrounding areas, it's more likely to be post-production. The range CGC gives for ink missing is 6.0-9.8 depending on severity. I'd call this a 7ish book. Maybe one would get lucky & score a higher grade, but I don't think the potential high end expectation would justify rolling the dice on grading.