How to create bootable installer
I think the documentation saying MacOS 10.11.6 is wrong as I can't figure how to run that as well. You may need to have a friend run the installer and send you the USB drive with bootable media or perhaps try one last time to reinstall 10.11.6 from this link:


http://updates-http.cdn-apple.com/2019/cert/061-41424-20191024-218af9ec-cf50-4516-9011-228c78eda3d2/InstallMacOSX.dmg


Sometimes re-installing the same combo updater fixes edge cases or some bit rot / rare damage to existing files. Just because your OS says 10.11.6 doesn't mean everything is in perfect running order.