Right now, if the VIPs have IPv6 listed first in the list of addresses, but the network fields like machineNetwork, clusterNetwork or serviceNetwork contains IPv4 primary address, the installation would progress and the bootstrap would end failing.
A validation needs to be included to ensure all required fields are IPv6 primary.

Change would likely be implemented here https://github.com/openshift/installer/blob/master/pkg/types/validation/installconfig.go#L241