Well, this way they could install dependencies anyway just automatically, so you don't see them unless you read before accepting the installation. I still can read this:

Install and configure the necessary dependencies
sudo yum install -y curl policycoreutils-python openssh-server perl

And then:

Add the GitLab package repository and install the package
curl https://packages.gitlab.com/install/repositories/gitlab/gitlab-ee/script.rpm.sh | sudo bash

So they do some magic here, the script just installs the repository, so I can't see exactly any dependency they are currently using.