The installation package ships a GFORTRAN module which does not declare a module version number. That number is needed to establish the proper prerequisites for binary rebuilds.
For more information please consult:
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 ea05801. For merge requests, please use the latest version in the Lintian check languages/fortran/gfortran.