The source tarball contains prebuilt doxygen documentation. This is usually left by mistake when generating the tarball without first cleaning the source directory. You may want to report this as an upstream bug if there is no sign that this was intended.
It is preferable to rebuild documentation directly from source.
The tag is present in Lintian version
That is the most recent version we know about.
We use semantic versions.
The patch number is a commit step indicator relative to the
release tag in our Git
You can find the detection logic for this version at commit ca97c3a. For merge requests, please use the latest version in the Lintian check documentation/doxygen.