The tag is present in Lintian version 2.104.232. That is the most recent version we know about.
The copyright file refers to
/usr/share/common-licenses/BSD. Due to the brevity of this
license, the specificity of this copy to code whose copyright is held by
the Regents of the University of California, and the frequency of minor
wording changes in the license, its text should be included in the
copyright file directly rather than referencing this file.
This file may be removed from a future version of base-files if references to it drop sufficiently.
Refer to Debian Policy Manual section 12.5 for details.