The tag is present in Lintian version 2.104.328. That is the most recent version we know about.
debian/control or a
.dsc file, the Source field
must contain only the name of the source package. In a binary package,
the Source field may also optionally contain the version number of the
corresponding source package in parentheses.
Source package names must consist only of lowercase letters, digits, plus and minus signs, and periods. They must be at least two characters long and must start with an alphanumeric character.
Please refer to Debian Policy Manual section 5.6.1 for details.