The article is painful to read. For one thing, the author comingles the GUI terminal app with the shell, which are distinct things. A GUI terminal doesn't need

The article is painful to read. For one thing, the author comingles the GUI terminal app with the shell, which are distinct things. A GUI terminal doesn't need to run a shell, even if often it does. e.g. "xterm -e emacs", now the GUI terminal is running emacs, not any shell. (Of course arguably emacs is a shell and a universe onto itself but different topic.) And a shell is called a "shell", not a "shell language". Yes a shell can be used as a scripting language, but when used interactively it is called a shell.