As the doc states, AKS now defaults to a Standard SKU load balancer. It is likely that this functionality was changed since Dec 2019. I tested this using
az aks create --resource-group RGName --name myAKSCluster --node-count 1 --vm-set-type VirtualMachineScaleSets --api-server-authorized-ip-ranges 73.140.245.0/24 --generate-ssh-keys
and the resulting Load Balancer:
"loadBalancerSku": "Standard",
If you see different functionality from current deployments, please let me know.