Rick Pildes has written more on Caperton, framed as a response to Linda Greenhouse.
I would add that vague pronouncements from the Supreme Court play another role as well: giving the Court the ability to see various approaches to its holding through natural variations in the lower courts. After getting more data, the Court can then settle on a firmer rule. That’s the point I make in Chapter 2 of this book. Whether Caperton motions will become common in the lower courts remains to be seen.