When powering on a VM, the autosizer will count the number of cores per pNUMA node (or threads if numa.preferHT is set), if the number of vCPUs is below that number, one NUMA client (PPD, scheduling construct) and one vNUMA node (VPD, guest visible topology) is created. If it is above that number, it will create an appropriate amount of PPDs but only create VPDs if vCPUs => the amount in numa.min.vcpu (defaults to 9, not 8).
So somewhat yes that there is a minimum, no to the at least 8 and maybe yes depending on what parameters you refer to