The tag is present in Lintian version 2.104.232. That is the most recent version we know about.
The installation package ships a GFORTRAN module but does not depend on gfortran-mod-<n>, where <n> is the module version (e.g. gfortran-mod-14 for modules built using GCC 5).
Refer to Bug#796352, Bug#714730, and https://salsa.debian.org/science-team/dh-fortran-mod/blob/debian/master/dh_fortran_mod.in for details.