Final answer:
The specification 'Fresh never frozen' is not a standard for custom cut sirloins as sirloins can be both fresh and previously frozen; other specs include 1/2-inch fat cover, CHOICE beef grade, and a maximum of 21-day shelf life.
Step-by-step explanation:
The specification that is not a standard for custom cut sirloins is C. Fresh never frozen. While the freshness of sirloin is a quality factor, the specification of being 'never frozen' is not a standard for custom cut sirloins as they can be both fresh and previously frozen. The 1/2-inch maximum fat cover is a specification for ensuring there is not too much fat on the cut. CHOICE beef refers to the grade of the meat, which is a quality standard by the USDA judging tenderness, juiciness, and flavor. The specification of having a shelf life of 21 days maximum is concerned with the freshness and safety of the meat before it should be sold or consumed.