Bash scripts can't be idempotent because they operate in an external environment that can't ever be. The better option is to just be extra safe.
The article is about writing bash scripts that don't care if you've ran them once, or 10 times.
set -o pipefail
Anything else I'm missing?
Is the idea that participants don't know what "idempotent" means in a thread with that word in the title?
Learn to handle errors, don't learn to brute force your way through them.