The configuration documentation has this phrase: "Once OSBS gains support for multiple architectures" ...
... OSBS has support for multiple architectures now, so we should edit this part of the documentation.
Commit 649ff095 fixes this issue
Metadata Update from @lsedlar: - Issue set to the milestone: 4.2.3
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/pungi/pungi/issues/1396
Please continue any further discussion there.