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.

Having a layer or two above the interface aware of the constraint works the best (when possible). Line based approach does this but requires agreement on the character (new line).

Also, it's not just the work needed to actually handle the write on the backend - even just making that many syscalls to /dev/null can kill your performance.