All reports of systemd-service-alias-without-extension for the archive. The extended description of this tag is:
The service file lists an alias without a file extension.
The spec mandates that the extension of the listed alias matches the extension of the unit itself.
Refer to http://www.freedesktop.org/software/systemd/man/systemd.unit.html#Alias= for details.
This tag has not been emitted in any package tested by Lintian.