Why are interfaces being configured with IPv6 options even though IPv6 is disabled at grub?

Issue

• When installing a new RHEL 7 system we see IPv6 options in the configuration files even though IPv6 has been disabled at grub

[root@rhel7u5 ~]# cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-3.10.0-862.3.2.el7.x86_64 root=/dev/mapper/rhel-root ro rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap console=ttyS0 LANG=en_US.UTF-8 ipv6.disable=1

[root@rhel7u5 ~]# cat /etc/sysconfig/network-scripts/ifcfg-ens9 
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=dhcp
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=ens9
UUID=7f9b8efc-7e16-4bd9-887f-f52fbda6884c
DEVICE=ens9
ONBOOT=yes