The Metadata import has two options JSON and XML in 2.39, previous there were 3 options JSON, XML, and CSV in 2.38.1 and below.
Though the TEI, Event, and Data Imports have all three options JSON, XML, and CSV.
It appears inconsistent from the implementation point of view, I think teams should have the option to work with either JSON, CSV, or XML files during the export or import of metadata.