Packer does not clear authorized_keys when using ssh_private_key_file (using vsphere-iso builder plugin)

We use the vsphere-iso builder plugin to create a RHEL based VMware template image, which works great. Our kickstart script includes the public part of the ssh-key into /root/.ssh/authorized_keys and packer is able to login afterwards via SSH.

However, the public key is not removed from authorized_keys afterwards, even when instructed to do so:

  communicator         = "ssh"
  ssh_username         = "root"
  ssh_private_key_file = "/home/packer/.ssh/id_ed25519_packer"
  ssh_timeout          = "20m"
  ssh_keypair_name     = "packer_buildhost"
  ssh_clear_authorized_keys = true

The contents of /root/.ssh/authorized_keys after image creation still remain as follows:

ssh-ed25519 AAAAC3...redacted... packer_buildhost

Which should match the ssh_keypair_name setting. We even tried adding temporary_key_pair_name to the configuration with the same value, but no better result.

Please advice me if I’m doing something wrong here, or if this might be a bug?
Thanks in advance!