Unable to set the right FQDN

Hi,
I've fallowed this guide https://docs.ovh.com/gb/en/public-cloud/changing_the_hostname_of_an_instance/ but doesn't work.
The file /etc/hosts will be always modified. I can disable this behavior only if I remove the line
- update_etc_hosts
from the cloud_init_modules

Here is now my /etc/hosts file
127.0.0.1 localhost

::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

127.0.1.1 myhostname.mydomain.it myhostname

But this is what I get
$ hostname --fqdn
myhostname.mydomain.it

$ hostname --all-fqdns
vps-xxxxx.vps.ovh.net

A tool that I've installed in this VPS finds this as FQDN myhostname.openstacklocal
Why I can't get always myhostname.mydomain.it?