Thanks a lot for your feedback, I will let our documentation team know about it so they can include it in our guides.
Regarding the error that you receive, please note that a previous step requires to clone the git repository from GitHub:
git clone https://github.com/aws/efs-utils
Then the AWS instructions omit the step to move the working directory into that repository:
build-deb.sh should be available. Could you check if building and installing the .deb package works?