> come up with a minimal and self-contained reproducer, so that someone who does can try it and see what you see on your end. So far you have only provided some terminal invocations accompanied by error messages and vague descriptions of comparing the actual and expected output of pg_dump.
Did you miss my e-mail starting with "After taking a longer break from my problem, I have now made a fresh, clean, scientifically conducted experiment in order to truly get to the bottom of this annoying problem once and for all."? (I don't now how I'd link to it.) There I go through everything with full commands and a minimal test database (which I also describe how I created).
I don't see how I could possibly create a smaller or clearer example of the issue. Whatever "strange things" cmd.exe does clearly doesn't show up for my cross-platform PHP CLI script. (I guess it's theoretically possible that PHP for Windows does some sort of "processing" automatically which pg_dump lacks, but I doubt it.)