Looking at that document, the entire metadata document is a single value in one row of a table!
I suppose that this is also how metadata is stored in a fileGDB? I don’t know the internals of fileGDB, but FME grabs the metadata as geodb_metadata_string, which is extremely long
geodb_metadata_string is an XML representation of the metadata of your FGDB. This goes in the ‘metadata’ column, you can specify XML in the ‘mime_type’ column.