Yeah, I don’t think there are many benefits when keeping the key on the same drive. Other than a bit of obfuscation. It does still help with erasing, as you can wipe the keyslots (rendering the key useless) but with modern storage media deletion is fairly hard to ensure. But still better than unencrypted.
YAML is fine as a configuration language and ok data input language.
YAML is absolutely cursed as a programming language. As in Ansible has created a really shitty programming language inside of YAML. Should be burned with fire.