Here's the current content of the Release file of Dev Edition Unstable:
Origin: neon Label: KDE neon - Dev Edition Unstable Suite: xenial Codename: xenial Date: Tue, 27 Jun 2017 02:53:22 UTC Architectures: all amd64 i386 Components: main Description: Generated by aptly
and the one in the user edition
Origin: neon Label: KDE neon - User Edition Suite: xenial Codename: xenial Date: Fri, 23 Jun 2017 15:56:52 UTC Architectures: all amd64 i386 Components: main Description: Generated by aptly
Notice that the only field to distinguish them is the Label, which is unreliable as it is pretty much subject to change than Suite and Codename. This causes issue when user tries to set up an APT Pinning to install certain package from the Dev edition stable or unstable archive, they have to setup like this:
# Only upgrade libqapt package from unstable dev archive Package: * Pin: release l=KDE neon - Dev Edition Unstable Pin-Priority: 99 Package: libqapt3 Pin: release l=KDE neon - Dev Edition Unstable Pin-Priority: 501
Either Suite: or Codename needs to be fixed according to their purpose, although I'm not sure what value is proper though.
According to apt_preference(5):
the Archive: or Suite: line names the archive to which all the packages in the directory tree belong. For example, the line "Archive: stable" or "Suite: stable" specifies that all of the packages in the directory tree below the parent of the Release file are in a stable archive. Specifying this value in the APT preferences file would require the line: Pin: release a=stable the Codename: line names the codename to which all the packages in the directory tree belong. For example, the line "Codename: stretch" specifies that all of the packages in the directory tree below the parent of the Release file belong to a version named stretch. Specifying this value in the APT preferences file would require the line: Pin: release n=stretch