Copyright of reference designs?

Your main confusion seems to be between copying a schematic and a design. Only the schematic is and can be copyrighted. It's only the drawing itself that is copyrighted. You can't, for example, copy the schematic of the reference design into a book of schematics and sell the book.

However, there is no restriction in the document of the idea behind the drawing. Ideas can't be copyrighted. They can be patented, but that's different from the copyright you asked about. Since the intent of TI in providing a reference design is for their customers to use it, it would be very strange if TI patented the design and then prevent you from using it. They want you to use their IC in a circuit, and many circuits will have significant similarities with the reference design.

Put another way, TI is giving their idea of how to use this chip freely, but not that specific drawing describing the idea. You are free to create your own drawings that describe the same or similar ideas.

All manufacturers provide explicit license information regarding reference designs and other resources (datasheets, app notes, ...).

For TI, in particular, it is in this document. It starts by saying:

Texas Instruments Incorporated (‘TI”) technical, application or other design advice, services or information, including, but not limited to, reference designs and materials relating to evaluation modules, (collectively, “TI Resources”) are intended to assist designers who are developing applications that incorporate TI products [...]

Then, later:

You are authorized to use, copy and modify any individual TI Resource [...]

But actually, this document is mostly a disclaimer from TI. It quickly says you can use the resources, and goes into extended lengths of explaining that you should not sue TI for whatever reason you might think of...

So, as Eugene said, the copyright you saw only applies to the resource document itself, not to the information given in the resource document.

Reference designs are intended to be copied and the manufacturer provides them with this intention.

It's not a substitute for reading the datasheet thoroughly, but it's also a pretty good way to ensure you're not too far off base with a complex design. In some cases you may even want to copy layout, for example for DDR memory to processor connections.

However, there is usually a disclaimer that indicates in legalese that you may be infringing someone else's patent by using the circuit and they take no responsibility for that.