You're talking about shebangs in general. This is about a specific shebang idiom, i.e #!/usr/bin/env python3 which allows the file to be run with whichever

You're talking about shebangs in general. This is about a specific shebang idiom, i.e #!/usr/bin/env python3 which allows the file to be run with whichever python interpreter the user has in their PATH, instead of requiring the interpreter to be in a particular location.