That's because, as a MacOS user, you are probably using the Z shell, not the Bourne Again shell. Prompt syntax is specific to each individual shell program.
One cannot just blindly use a Stack Exchange Q&A that states that it is for "Linux" and "bash" on the Z shell on MacOS, or indeed on the Z shell on a Linux-based operating system for that matter. Or in the C shell. Or in the Korn shell. Or in the Watanabe shell.
One cannot just blindly use a Stack Exchange Q&A that states that it is for "Linux" and "bash" on the Z shell on MacOS, or indeed on the Z shell on a Linux-based operating system for that matter. Or in the C shell. Or in the Korn shell. Or in the Watanabe shell.