If I were to make an assumption, I would say that the decision to shorten it came probably about a week or so before we found out, since it was pretty clear the Bleeding Cool article was not something they were anticipating and more likely than not wanted to keep the Bat/Cat book a surprise until the 2020 solicits, rather than announce it half a year in advance. The announcement he was writing New Gods came about a week after the initial article too, so presumably that was when their talks and discussions about him taking the job were solidified, so by then is when had just a few months to start tweaking everything.