The point is to attract new Patreons. The rule is that new patreons get a copy after 30 days.
Public announcement is not part of that agreement, but a matter of the author's decision, he can make a decision on public announcement even before the expiration of the 30-day period, as he will do here. The patronage relationship is not the same as the relationship between buyer and seller, or the relationship between owners of shares in a company. The decision on the artwork is made by the author. Why the author made such a decision can be read from this graph:
The day after the publication of this post,
Times are rough for us all, these days... We could all use a little hope...
therefore, on October 26, the support (patreons - 223) began to grow rapidly. On October 30, it grew to 256, and on the 31st, no one new joined.
By continuing to insist on rigid rules of announcement, you're not bringing in new Patreons, you're just driving potential new ones away. This is just my assessment, i am not patreon nor do i participate in the decisions or advise the author.
If the new sequel is as perverse as the changelog promises: (New optional fetishes: Pregnancy, smegma, rimming.) There is no doubt that after the public announcement, the number of patreons will grow. By postponing the public announcement at this time, the author is harming his interests. It is better to have money today than tomorrow.