1832 Classic Head Half Cent ANACS AU Details EF45 Corroded

So, I'm not one to question grading...usually. Corrosion, scratches, rim damage, cleaning - almost always easy to spot with a 30x loupe. I have to admit - on this one I'm not seeing any corrosion. There's no black holes or green spots or green within the circulation dings or anything that I normally associate with corrosion. That's not to say it's not there - ANACS isn't dumb. It's just weird that I don't see it.
This is really a beautiful coin. There's just a hint of red still showing in all the high details and it's truly as close to UNC condition as you can get.