Any publicly available evidence to back that up? There have been post-exit blog posts from OpenAI employees on HN before and it did sound like the only black magic they use there is that many employees work 16 hrs a day during launch of new features. I know that some current Claude Code devs are doing interviews where they claim that they use Claude Code extensively but they clearly have a conflict of interest while they are still employed at Anthropic, so it would be like asking a barber if you need a haircut.

Look at the number of features (PRs) being pushed by these companies.