It's important for all of us to remember that blockchain technology is still brand new. Amazon is aware of it, but I don't think they've put any policies in place pertaining to it specifically. The 10,000-word guideline is publishing standard, typically, before they consider a work to be unpublishable as a first edition. This isn't a hard and fast rule, but it should certainly influence decisions.

It's entirely possible that Amazon could eventually deem everything on the blockchain to be "published" regardless of word count. We'll just have to wait until the first big issue arises and see how they handle it. I, for one, do NOT want to be that first big issue.