@Switch Blayde
Yes, and that's true even if it's for sale elsewhere
As I wrote before, no, it is not.
Author Agreement paragraph 17A:
Any promotional links or text to sell your complete books are allowed only if they point to our book shop ZBookStore.com. Progress must be made at least bi-weekly until the work is complete on Storiesonline.
Now, the size of those bi-weekly updates is not defined, but from what I see on the site so far, it seems that, as long as the "last updated" date on a story isn't older than two weeks, you're golden. So, as long as you post a single sentence every two weeks, you can sell the completed work on bookapy/zbookstore for years.
However, if the story is completed on an EXTERNAL site, like a Patreon page or your own story site, suddenly, your story on SOL must be completed WITHIN two weeks, or it constitutes "teasing" (according to Paragraph 17C of the very same Author Agreement):
[...] You must keep the work on Storiesonline within two instalments of the work on the support site. If the work is completed on the support site, then it must be completed on Storiesonline within two weeks of the completion on the support site.