Oh, I didn’t realize that this was in the Juju documentation.
I think that this is misleading and, frankly, incorrect, given that there is not a much better alternative to using base64 encoding if you want to be able to export a bundle.yaml with structured config in it.
I think that should probably be changed. Simple config is fine, but if an application needs complicated configuration, piping it through the overly restrictive simple config is not going to make it any simpler.