Why does it matter? Tbh at this point if frontier models are used I would place more trust in the average codebase than the average pre-AI codebase.
There are outliers where an excellent team of devs produce great quality, better that even frontier LLM code now. SQLite comes to mind. But it's easy to forget that is the 0.x%.
the comment isn't even about the quality, it's about the "from scratch" aspect (used to 'market' it)