The tag is present in Lintian version 2.104.232. That is the most recent version we know about.
The source tarball contains a waf binary. This file is a Python script with an embedded bzip2 archive, which is uncompressed and unpacked at runtime.
Although corresponding sources can be easily extracted, FTP Team does not consider waf binary as the preferred form of modification; it should be provided unpacked instead, or completely removed, if possible.
You might want to follow these guidelines to obtain an unpacked waf: https://wiki.debian.org/UnpackWaf