This is a fairly reasonable explanation, that is somewhat marred by two things.

First, the suggestion to demonstrate non-canonical input mode with the stty command will not work for many people. Many shells that have command-line editing save and restore the termios settings before and after reading each line of interactive input. Run stty raw and stty sane from the Z shell, for example, and nothing at all will apparently change when typing input to ZLE. The same goes for the Bourne Again shell and Readline.

Second, it keeps talking about a "local PTY device". The local end has a terminal, but that is not necessarily a pseudo terminal. It could be a real terminal, or a kernel virtual terminal.