When DataLad Catalog is fed with json lines (catalog add), it will
write their content to files inside a catalog instance, updating or
extending already stored content. So it is not a copy of what was
added, but rather a further derivative and an amalgam of different
additions.
Q: "Why and how is the metadata that adheres to the catalog schema different from the metadata in a functional catalog?"
Comment by @mslw in https://github.com/psychoinformatics-de/rfd/pull/68:
To be explained somewhere in the docs.