It would be better to hear an official response from Epic, but yeah. Epic uses macros, along with templates, the build tool, and so forth, to hide necessary chunks from people who shouldn’t be touching them. Macros are difficult to debug, but it’s all things that you shouldn’t need to debug in a project. If it doesn’t work, then it’s Epic’s problem to fix on the engine side.
Of course, they give you source access too, so you are free to fork Epic’s side to suit your needs. They’ll hide things from typical users, though.