Hello,
SetUserSSHPublicKeysPlugin is always populating ~/.ssh/authorized_keys with public key (if provided).
but this path is incorrect for Administrative users.
as explained here: https://learn.microsoft.com/en-us/windows-server/administration/openssh/openssh_keymanagement#administrative-user

authorized keys for Administrator user should be stored in C:\ProgramData\ssh\administrators_authorized_keys, not in C:\Users\username\.ssh\authorized_keys.

this bug results in inability to connect using ssh key authentication as Administrator even when correct public key was provided to SetUserSSHPublicKeysPlugin.