Maybe they machines are listed as soon as they are received by apple and the shipping date is put there to allow for apples refurbishment program...
"Each Apple Certified Refurbished Product:
is fully tested (including full burn-in testing).
is refurbished with replacement parts for any defective modules identified in testing.
is put through a thorough cleaning process and inspection.
is repackaged (including appropriate manuals, cables, new boxes, etc.).
includes the operating software originally shipped with the unit and the custom software offered with that system. See each products "Learn More" for more details.
is given a new refurbished part number and serial number.
is placed into a Final QA inspection prior to being added to sellable refurbished stock."
Although it does say:
"Apple Certified Refurbished Products are pre-owned Apple products that undergo Apple's stringent refurbishment process prior to being offered for sale."