this is basically talking about compilers and things like dumping a memory image from gforth or emacs

if someone said 'no, the output from my gpl-licensed compiler is never covered by the gpl', then would-be infringers would have an easy escape from the gpl: just compile the compiler with itself, and its author guarantees that the compiled output isn't covered by the gpl! so that's why the fsf carefully says 'only if the output, given its content, constitutes a covered work'

similarly, emacs or gforth has the ability to dump a memory image after loading up a bunch of source code and compiling it to bytecode; that way it can instantly load the image without taking the time to recompile all that code. this memory image includes all the code that's loaded, including not just your code, but also all the standard library code that comes with the system. but that shouldn't give would-be infringers an easy escape from the gpl for the standard library code