It was found here https://github.com/openSUSE/libsolv/issues/450 that upstream has a -W flag which allows you to cleanly parse debugdata generated by --debugsolver and see the dependency chain which pulls in a package.

# yum install httpd --debugsolver
# cd debugdata
# testsolv -W mod_http2 rpms/testcase.t
<I dont have this output handy but it shows that httpd requires mod_http2>


This would be very helpful in the RHEL space for debugging complicated transactions if we can implement it.