I do a lot of research into court cases. If you consider the large number of patterns produced by McCalls, Butterick, Vogue and Simplicity, just the large companies, there is not one federal lawsuit that has gone to trial that involves the use of their patterns that I can locate. One reason is the lack of registered copyrights by them. Also, anyone who decides to get into commercial use of a design will have patterns done professionally for their machines.
Quilting patterns require much more originality and effort than the clothing patterns marketed by the big companies. But it still comes down to what the copyright office says is a requirement for registration: originality. While arranging blocks may constitute some originality, the final design must be original enough to qualify for registration. I have not found a single federal court case where an unregistered design has won in court.
This is the most polite board I have seen. Everyone here discusses the subject without getting personal. That is refreshing to see.