It appears that @ignatenkobrain got some changes into the texinfo package back in February which add the following file triggers:

%transfiletriggerin -n info -- %{_infodir}
[ -f %{_infodir}/dir ] && create_arg="" || create_arg="--create"
%{_sbindir}/fix-info-dir $create_arg %{_infodir}/dir &>/dev/null

%transfiletriggerpostun -n info -- %{_infodir}
[ -f %{_infodir}/dir ] && %{_sbindir}/fix-info-dir --delete %{_infodir}/dir &>/dev/null

which, if I understand the function of fix-info-dir correctly, means that it is no longer to call install-info when installing info pages on F28+. (My undrestanding of fix-info-dir is that it will go over the existing info files and call install-info on them if they are not already listed in the dir node, which is exactly what's needed here.)

If I'm correct, we can add an "F27 only" bit to https://fedoraproject.org/wiki/Packaging:Scriptlets#Texinfo and then move it to the EPEL guidelines in another six months or so. That doesn't really take a vote as it's just reflecting reality, but I wanted to make sure my understanding of the situation was correct.

Finally, as we do this, we should consider convenience macros in the vein of what we did for ldconfig which eventually would do nothing in Fedora but which could be used for EPEL in place of piles of conditionals. And if I had time I'd just sit down and write them.

Edit: Also, rpmlint will need to be told to shut up about "info-files-without-install-info-postin" (and s/postin/postun).