If I looked at what this does and none of the surrounding discussion/documentation, I'd say this is to simplify using secrets manager properly more-so than any security purpose.

To use secret manager "properly", in most cases you're gonna need to pull in the entire AWS SDK, maybe authenticate it, make your requests to secret manager, cache values for some sort of lifetime before refreshing, etc.

To use it "less properly", you can just inject the values in environment variables but then there's no way to pick up changes and rotating secrets becomes a _project_.

Or just spin this up and that's all handled. It's so simple you can even use it from your shell scripts.