[anyoan1]

Are ACS Grades suitable for food application?
Usually ACS Grade seems to be more pure on the paper.
Why when something is ACS doesn't automatically make it FCC Grade even though it has stricter specifications, often overlapping.
Is it just a legal safeguard by manufacturers?

[Borek]

Why when something is ACS doesn't automatically make it FCC Grade even though it has stricter specifications, often overlapping.

Because they were not defined this way in the law. Legal rules are blind and have to be followed to the letter, even if the logic suggests otherwise.