The tag is present in Lintian version 2.104.328. That is the most recent version we know about.
The control file has a Build-Depends, Build-Depends-Indep, Build-Conflicts, or Build-Conflicts-Indep field in a binary section. These specify source package relationships, and should be in the source section of the control file.
Please refer to Debian Policy Manual section 5.2 for details.