From the U.S. Copyright Office: "Copyright does not protect ideas, concepts, systems, or methods of doing something. You may express your ideas in writing or drawings and claim copyright in your description, but be aware that copyright will not protect the idea itself as revealed in your written or artistic work."
As a designer myself... I agree. There are many traditional quilt blocks that have been around for centuries (that in itself places them in the public domain). Not only that, you can find certain designs in different cultures. Who is to say who came up with the idea first? Ideas are in fact a part of our collective consciousness as the human race.
In this case, what is protected is the kit itself, along with its instructions. This has happened to me several times with tutorials. The objective of a tutorial is to teach something... a method or idea. If somebody takes that idea and turns around and teaches it to somebody else, that is fair game. What that person cannot do is take my written instructions and photos/illustrations and use them as her/his own.
Does this help? I do think it is too bad that this whole copyright issue has tended to make quilters a little paranoid. Even though I design myself, I certainly wouldn't want fellow quilters to feel stifled about letting their own creativity lose! However, when in doubt, it is always best to ask. Even though designers do not always have things clear, either.
If you Google "copyright" you will find many articles covering the topic that might shed some light for you.