This has nothing to do with AWS! I'm aware that elastic is available on other cloud providers :) this is an on premise alternative to S3.
The scripts embed Amazon dependencies don't they? If I mis label this as AWS depending, can you explain how I use this to do a dump on a gcp hosted es instance?
I think you just missed the purpose of the article! It simply explains how to backup your es indices on minions, which is a S3 alternative and that's why the use of s3 plugin! There are different plugins for different cloud providers that's above the scope of the post!