While it is understood, that the `networking.machineNetwork` parameter is not required [1] for bare metal UPI and generally `platform: none`, nevertheless it does make sense to include it in the sample `install-config.yaml`. On the one hand to be a bit more consistent with other installer samples, like ABI [2]. On the other hand, you cannot change this parameter post installation, thus it makes sense to highlight the implication. Lastly `fips` is also not a required parameter for the `install-config.yaml` and still it is present [3][4].
The `install-config.yaml` sample could be improved, if we would include `networking.machineNetwork` with a corresponding note despite being optional.

Please note, that when missing out on the `networking.machineNetwork` setting, it will be required to take care of it during cluster-wide proxy configuration [5].

[1] https://docs.openshift.com/container-platform/4.16/installing/installing_bare_metal/installation-config-parameters-bare-metal.html#installation-configuration-parameters-network_installation-config-parameters-bare-metal
[2] https://docs.openshift.com/container-platform/4.16/installing/installing_with_agent_based_installer/installing-with-agent-based-installer.html#installing-ocp-agent-inputs_installing-with-agent-based-installer
[3] https://docs.openshift.com/container-platform/4.16/installing/installing_platform_agnostic/installing-platform-agnostic.html#installation-bare-metal-config-yaml_installing-platform-agnostic
[4] https://docs.openshift.com/container-platform/4.16/installing/installing_bare_metal/installation-config-parameters-bare-metal.html#installation-configuration-parameters-optional_installation-config-parameters-bare-metal
[5] https://docs.openshift.com/container-platform/4.16/installing/installing_bare_metal/installing-bare-metal.html#installation-configure-proxy_installing-bare-metal

    4.16+

    In case of Baremetal UPI cluster installation, the `networking.machineNetwork` parameter is not required during installation, as it is the responsibility of the user only for providing and configuring the infrastructure, including networking, outside of what the OpenShift Installer directly manages. This includes setting up IP addresses, routes, DNS, and other networking components on your own, without relying on the installer to configure these settings. Since the user has direct control over the infrastructure and networking configurations of the machines, the Installer does not need to manage or be aware of the specific network configuration.