Do you expect them to release a July 4th themed product on July 3rd? No, they do it a month or two ahead to maximize sales. Besides, no one will buy them on July 5th.
Those things are chock full o' preservatives anyhow, so they could have put them out 6 months in advance.
Same thing with any holiday themed or special sale product. I guarantee that retailers have their "back-to-school" ads printed and merchandise ready to put on the floor on July 5th.