Thanks in advance!
ETA: Success! Sort of.....
So I made the cookies and the ground tapioca worked perfectly. They had a springy texture, though a bit puffier than I was expecting. I'm not sure what everyone else's experience was, but I faithfully followed the recipe nearly to the end and decided there was no way that what I had in front of me was going to make cookies. There is a LOT of liquid in this recipe, making it very gloopy and nearly the texture of cake mix after all the flour was added. I decided to go for another half cup of flour and it worked out fine. They are very, very oily, however. Like, the chocolate chips were falling out of the dough, oily. I had to carefully shove chips back in to each spoonful before baking, but they came out fine and not as greasy as expected.
As for flavour, I didn't think they were that interesting. I'll definitely try the recipe again, but I think I'll add more vanilla and maybe a bit more salt for richness.