My mistake is obvious - now. But I didn't notice it until the block was sewn, pressed, and laying alongside the big version. Oops!
The big block is Winter Star from the Farm Girl Vintage book. The little block is what happens when the "slanted" sections are sewn together wrong. I should have matched the sides with the lower part of the slant, but did it just opposite. And it's interesting how that creates a whole new block.
The result is still pretty nice and I'm NOT going to take it apart to fix it. These may - or may not - even end up in the same quilt, so it really doesn't matter in the long run.