When Nova creates a new VM, it uses the name the user has configured as the libvirt machine name. Due to a libvirt limitation, this name can never change, however the user can change the Nova name. If this happens, we are left with this situation:

<domain type='kvm' id='3'>
  <name>instance-00000074</name>
  <uuid>6932a1f3-b07b-4b68-8e35-58b5a38ed8de</uuid>
  <metadata>
    <nova:instance xmlns:nova="http://openstack.org/xmlns/libvirt/nova/1.1">
      <nova:package version="23.2.3-17.1.20231018130823.el9ost"/>
      <nova:name>kincho-test-4</nova:name> 

Whereas Ceilometer always retrieve the name from the libvirt instance name field, as we can see in https://opendev.org/openstack/ceilometer/src/branch/master/ceilometer/compute/pollsters/util.py#L37

This is a bug, as Ceilometer should be retrieving the name always from the nova:name field. That would keep the labels of the metrics aligned with the desired user's VM name.