Well - the question becomes were the spots there or not when it graded? I don't know. There was one before that was worse. So who knows.
You guys give the reverse too much credit, IMO. Grade the obverse a grade, and unless there's something ridiculously wrong for the obverse-assigned-grade, keep that grade. As for if that spot was there or not, who's to tell. It does have the look of the types of spot that sometimes grow inside the slab (that greyish color). It's an old NGC slab, too, meaning it's had quite a bit of time in that slab.
p.s. I also undergraded the coin, thought the graders wouldn't have liked the symmetrical hits on the face.
I think my initial impression is becoming a little more liberal. I'll know I've zeroed in on things when I'm higher or lower at the same rate, then it's just a matter of precision rather than initial grading bias.