I agree that this system could be misleading. There must be some management consultant that has been selling this because we had this format for our yearly personnel performance evaluations. A Viking program director suggested that we fill out the boxes A, B, C, D style. We always give the top rating unless there was something specific, even though this is exactly what we expect.
An important thing to remember though is to recognize exceptional crew members by name, this affect their promotions and opportunities.