I had not done a git pull on the docker setup script recently. I am one of those backward people who appreciate versioned releases of software and frown at developers who only support the latest git commit. (I do not know nor claim whether this is the case for the Discourse Docker installer, yet, though it is the first impression I got).
Indeed the installer script looks much better on the latest commit and should work with single server installations. It would not reliably work in a load balancing scenario where HTTP(S) requests to a single IP address may end up on different servers to the backend (LB pool). But I do not know whether this scenario is even supported at this time.