The real reason they aren't releasing it yet is probably it eats TPU for breakfast, lunch, and dinner and inbetween.
How about "bad agents acquiring dozens of new zero-days and using them to compromise any company or nation they want"? It's not exactly hard to see why you wouldn't want public access to a model significantly better than Opus in cybersecurity.
The real reason they aren't releasing it yet is probably it eats TPU for breakfast, lunch, and dinner and inbetween.