No, as you already mentioned, that is the expected behavior. You may have a look into the similar question about Module user WARNING:Found existing ssh key here.
I think the only option is to disable in Ansible Configuration Settings the ACTION_WARNINGS
By default, Ansible will issue a
WARNINGwhen received from a task action (module or action plugin). These warnings can be silenced by adjusting this setting toFalse.
by setting in example
grep 'defaults\|warnings' ansible.cfg
[defaults]
deprecation_warnings = False
action_warnings = False
and then resulting into an output of
TASK [ansible.builtin.user] ******************
ok: [localhost]
PLAY RECAP ***********************************
localhost : ok=1 changed=0