VirtualBox docs result in SSH password prompt

[tlhunter]

I've followed the following guide:
https://coreos.com/os/docs/latest/booting-on-virtualbox.html

This is when using VirtualBox version 6.0.10 r132072.

Specifically I followed the steps to download and run create-coreos-vdi, then I followed the same instructions for create-basic-configdrive and used the example arguments and my non-password-protected public key. I also ran the VBoxManage commands (though I had to change the one command to VBoxManage clonehd coreos_production_2135.6.0.vdi my_vm01.vdi as coreos_production_stable.vdi doesn't exist).

Finally I used the GUI to finish creating the machine following the instructions, selecting the new 10GB disk. I then enabled port forwarding using the recommended steps. However, when I attempt to SSH into the machine, I get a password prompt:

ssh core@localhost -p2222

The expected result is that my public key would satisfy the login attempt.