Jeff provides many different styles of blank to us. He follows the inventory and sales and replaces most patterns when they are "out of stock".
However, he is still only one person!! So, he allocates his time to make the blanks that are most popular. So, when one pattern goes "out of stock", he may choose to replace it, or use that time to create a new or restock a more popular pattern. In short, he optimizes the use of his time.
Particularly the scroll-sawn blanks require more time and don't have the more universal appeal of his newer blanks.
Like most products, newly-developed items sell more rapidly. What you are seeing is Jeff's product transition. The newer designs sell far more rapidly than most of the scroll-sawn. I'm sure you can understand he tries to make what will sell most quickly and a "batch" is typically a dozen or so.
Hope this gives you some understanding of the process.
Ed
