I still haven’t figured out exactly what was wrong with the trees, but as you can see, I did have some success in something. The logs in the picture above are rotated correctly! Huzzah!
Meanwhile, here are some screenshots I took a few days ago while the trees were still working:
Yesterday, I spent about an hour working on this mod. I got it so that the growth blocks will grow new trees with growth blocks on top. Unfortunately, they wouldn’t grow continuously, due to a bug that I know exactly how to fix, but didn’t have the time yesterday.