alt Hacker Newsthank you for all your irrelevant citations and speculations.
the question is still open if that guide is grounded into US legal landscape in any way. Unlike good quality legal literature which grounds every statement into law or case law, that guide does nothing.
The part "Copyright is another form of intellectual property protection available to code and algorithms. However, it should be noted that certain jurisdictions do not permit an owner to assert both trade secret and copyright, especially if the copyrighted software discloses a majority of the source code or the “proprietary” portions. (2)" provides a link to Capricorn Management Systems, Inc. v. Government Employees Insurance Co.
The decision can be read at https://cases.justia.com/federal/district-courts/new-york/ny...
That decision is about if something can be both a trade secret and copyrighted.