This is what i was told by my manager.
Summary:
A person with 'exceeds' might get the same appraisal as a person with 'met' expectations.
Explanation:
Person A and Person B might be on the same level - example grade 57.
Both are eligible for exceeds, but lets just say they can give it to only 1 person as they have to write an explanation to the leadership detailing why they picked either of them.
If Person A is given 'exceeds' by comparing the work between them, Person B might be upset not knowing why they didn't get 'exceeds' even though they put their sweat and blood into it. So they try to keep the $$ number around the same range and compensate both.
Ofcourse, this might have its own pros and cons. This is what I was told and understood. I got an exceeds btw.