This looks very interesting, however it seems to me like the critical piece of this technique is missing from the post: the implementations of getFileContext() and shouldStartNewGroup().
Reading between the lines, it sounds like they are creating an AI product for more than just their own codebase. If this is the case, they'd probably be keeping a lot of the secret sauce hidden.
More broadly, it's nowadays almost impossible to find what worked for other people in terms of prompting and using LLMs for various tasks within an AI product. Everyone guards this information religiously as a moat. A few open source projects are everything you have if you want to get a jumpstart on how an LLM-based system is productized.