If you're using custom authority types, automatic linking via C4::Biblio::LinkBibHeadingsToAuthorities will never work. It's because C4::Heading::MARC21 has a hard-coded mapping of bib fields to authority types (instead of consulting the MARC bibliographic framework). This means if you're using "CORPO_NAME_AWSEOME" instead of "CORPO_NAME" for your authorities, you'll never get an automated match, since C4::Heading::_search (used ultimately by C4::Linker::Default) uses the hard-coded auth_type from C4::Heading::MARC21.
I suppose that a fix could be done by looking up the framework thesaurus in C4::Heading::new_from_field and overriding the default hard-coded auth_type... (At a glance, LinkBibHeadingsToAuthorities seems to be used whether or not a framework thesaurus has even been defined. That's also... special... but that's a different issue for another day.)
We'd want to add some unit tests to t/db_dependent/Heading.t too for checking the correct auth_type...
That hardcoding in C4::Heading::MARC21 makes things more inflexible then I thought they would be...