LOL, well, I guess I’m going to disappoint you today. I tried though, but I suspect that the commit of this importer was incomplete and did not include some changes to base.rb. @justin worked on this, maybe he knows. I do suspect that this could have been a customer specific thing that can be commented out without further consequences.
I have never used the bulk importers myself either.
Yes, import scripts can be complex and depend on the database specifics, but some scripts are simply not in a working state. That goes for this one as well, and there are some more scripts with for instance # frozen_string_literal: true that are just not working out of the box.