Must be some pretty trivial software, since 90% of the code base is apparently class and function declarations filled with empty or pointless (get/set) OO garbage.
Some enterprise software, most of the patterns are well know and the customization point are well defined.
I would describe more as a well know domain with clear constraints than trivial software.
They generate a lot of code also for high critical real time software (avionics and space) but that is not really trivial.
I'm skeptical the code generators are used for the actual function bodies at any level. That's 90% of any non-trivial code, not function and class declarations and stubs.