Hi Viv!
Okay, I think I should start by mentioning the difference between a chapter, and a sequel. A sequel does not require the reader to read the prior work to read the sequel. In other words, a sequel can be read as a separate story. A chapter can't.
A chapter is NOT okay in the anthology, and it never has been, becuase the anthology is, as it has always been, a collection of short stories (every submission guideline we have ever had has specified "short stories"). Anthologies, by definition, are not collections of chapters, and the GA anthology won't be accepting any chapters for that reason. It would just kill off the format we have, as well as making things hard on the readers. So, that's something I had to draw the line at, and it won't be moving on my watch.
However, Viv's UTBOS hasn't been chapters so far; each has worked as a stand alone story. True, you get a better feel for it if you read the prior ones, but, that's true of most any sequel, and sequels are okay.
The only new rule, really, is the prohibition on using numbered titles like UTBOS 1, 2, 3, etc, BUT, there is an exception for people who were already doing so for the title they were using. So, UTBOS 5 is fine, so long as it, like the prior ones, works as a free standing story. Just don't call it a chapter.
CJ
Edit to add: The rule against numbered titles went into effect a few months ago, and as Viv was the only one doing numbered titles at that time, only UTBOS has that exception. For example, if I wanted to follow up by winter entry of "Three for Jake" with Three for Jake 2, I couldn't. Well, I could, but not in the anthology.