Buffers are there for good reason, it's extremely slow (relatively speaking) to print output on a screen compared to just writing it to a buffer. Printing something character-by-character is incredibly inefficient.

This is an old problem, I encounter it often when working with UART, and there's a variety of possible solutions:

Use a special character, like a new line, to signal the end of output (line-based).

Use a length-based approach, such as waiting for 8KB of data.

Use a time-based approach, and print the output every X milliseconds.

Each approach has its own strengths and weaknesses, depends upon the application which one works best. I believe the article is incorrect when mentioning certain programs that don't use buffering, they just don't use an obvious length-based approach.