docs: useradd issue

What happened?

I'm currently working through https://frankenphp.dev/docs/docker/#running-with-no-capabilities and see the line useradd -D ${USER}; mentioned several times.

Following through the example:

docker run -it --rm dunglas/frankenphp bash
export USER=www-data
useradd -D ${USER}

just prints the commands help.

-D for useradd is print or change default useradd configuration.
-D for adduser is Don't assign a password

From my understanding the intention is to add a user www-data without a password on debian? That would be useradd without specifying -p. But even then

cat /etc/passwd | grep www-data

show the user already exists, so can it be omitted because it serves nothing?

Build Type

Docker (Debian Bookworm)

Worker Mode

Yes

Operating System

GNU/Linux

CPU Architecture

x86_64

PHP configuration

The one installed in the docker image dunglas/frankenphp

Relevant log output

No response

Start at the linked Docker documentation section on running with no capabilities and verify the shown useradd command in the FrankenPHP Debian image. Compare the command's behavior with the existing www-data entry, then update the example so the instructions accurately reflect the required user setup and confirm the rendered documentation no longer shows misleading guidance.