Currently KubeMacPool range is applied on all VM interfaces, regardless of its binding type - masquerade, bridge, etc.
The pod masquerade interface is used only internally, i.e. to connect to the virt-launcher, and it "hides" behind the pod's interface. Therefore, it's redundant to apply the KMP it, as it consumes available MACs from the pool for no reason, and derives MAC conflict enforcement, which is also not needed.

CNV 4.21.0
container-native-virtualization-kubemacpool-rhel9:v4.21.0-31

100%

1.
On your cluster - check the configured KubeMacPool range (currently it appears in a dedicated ConfigMap, and supposed to be available in HCO later on):
$ oc get cm -n openshift-cnv kubemacpool-mac-range-config -o jsonpath={.data} | jq
{
  "RANGE_END": "02:a2:4f:ff:ff:ff",
  "RANGE_START": "02:a2:4f:00:00:00"
}

2.
Create a basic VM with only the default masquerade interface explicitly mentioned:
$ cat << EOF | oc apply -f -
> apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
metadata:
  name: vma
spec:
  runStrategy: Halted
  template:
    spec:
      domain:
        devices:
          disks:
            - name: containerdisk
              disk:
                bus: virtio
            - name: cloudinitdisk
              disk:
                bus: virtio
          interfaces:
            - name: default
              masquerade: {}
        resources:
          requests:
            memory: 1G
        cpu:
          cores: 2
      networks:
        - name: default
          pod: {}
      volumes:
        - name: containerdisk
          containerDisk:
            image: quay.io/openshift-cnv/qe-cnv-tests-fedora:41
        - name: cloudinitdisk
          cloudInitNoCloud:
            userData: |-
              #cloud-config
              password: password
              chpasswd: { expire: False }
EOF
virtualmachine.kubevirt.io/vma created

3.
No need to start the VM.
Check the MAC address that was assigned to the VM resource object:
$ oc get vm vma -o jsonpath={.spec.template.spec.domain.devices.interfaces[0]} | jq
{
  "macAddress": "02:a2:4f:d6:d4:93",
  "masquerade": {},
  "name": "default"
}

Assigned MAC is withing the MAC pool range.

Default masquerade VM interfaces can and should be assigned an arbitrary MAC address, which can also be similar in several (all) VMs, and not exhaust the MAC pool.