The tag is present in Lintian version 2.104.234. That is the most recent version we know about.
Ada Library Information (*.ali) files are required to be read-only (mode 0444) by GNAT.
If at least one user can write the *.ali file, GNAT considers whether or not to recompile the corresponding source file. Such recompilation would fail because normal users don't have write permission on the files. Moreover, such recompilation would defeat the purpose of library packages, which provide *.a and *.so libraries to link against).
Refer to Debian Policy Manual section 8.4 for details.