It looks like size 5-7 tips are not available. I bet they are just sold out of popular sizes. Weird way to express that though. I think if it was a quality issue, it would apply to more sizes. I just checked the Harmony sock DPN set, and it says available 9/28. I bet they are in the process of updating the site.
I just called their customer service number and they said those sizes are out of stock because they are "going very, VERY FAST" but as soon as they have them back in stock they will be back up on the website.