Can ssh-authorized-keys under users section be merged?

Question

I'm trying to merge the following multi part cloud-init file.

The runcmd and write-files are working perfectly, but I can't merge the keys on the ssh-authorized-keys of the root user.

Anyone knows how to do that?

Content-Type: multipart/mixed; boundary="//"
MIME-Version: 1.0
    
--//
Content-Type: text/cloud-config; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="cloud-config.txt"
Merge-Type: list(append)+dict(no_replace,recurse_list)+str()
#cloud-config'

hostname: ${hostname}
create_hostname_file: true
fqdn: ${fqdn}
prefer_fqdn_over_hostname: true
disable_root: false
users:
  - name: root
    ssh-authorized-keys:
      - ssh-rsa AAA... the_one_key
runcmd:
  - |
    touch > /home/lele.txt
    echo "lele" > /home/lele.txt
write_files:
  - path: /home/du.conf
    content: du

--//
Content-Type: text/cloud-config; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="cloud-config(2).txt"
Merge-Type: list(append)+dict(no_replace,recurse_list)+str()

#cloud-config

users:
  - name: root
    ssh-authorized-keys:
      - ssh-rsa AAA... the_second_key

runcmd:
  - |
    touch > /home/lala.txt
    echo "lala" > /home/lala.txt
write_files:
  - path: /home/ti.conf
    content: ti
--//--

Here is the content generated by cloud-init after merge

As you can see the users: section is been merged but just the first key is included on the /root/.ssh/authorized_keys file.

What I want is that cloud-init merge the keys on ssh-authorized-keys: list instead duplicate the root section.

#cloud-config

# from 2 files
# cloud-config.txt
# cloud-config(2).txt

---
create_hostname_file: true
disable_root: false
fqdn: vm-test.com
hostname: vm-test
prefer_fqdn_over_hostname: true
runcmd:
- 'touch > /home/lele.txt

    echo "lele" > /home/lele.txt

    '
- 'touch > /home/lala.txt

    echo "lala" > /home/lala.txt

    '
users:
-   name: root
    ssh-authorized-keys:
    - ssh-rsa AAAAB...
        the_one_key
-   name: root
    ssh-authorized-keys:
    - ssh-rsa AAAAB...
        the_second_key
write_files:
-   content: du
    path: /home/du.conf
-   content: ti
    path: /home/ti.conf
...