The real question is adoption friction. The annotation requirement means this won't just slot into existing codebases — someone has to go through and mark up every buffer relationship. Google turning on libcxx hardening in production with <0.5% overhead is compelling precisely because it required zero source changes.
The incremental path matters more than the theoretical coverage. I'd love to see benchmarks on a real project — how many annotations per KLOC, and what % of OOB bugs it actually catches in practice vs. what ASAN already finds in CI.
The WebKit folks have apparently been very successful with the annotations approach[0]. It's a shame that a few of the loudest folks in WG21 have decided that C++ already has the exact right number of viral annotations already, and that the language couldn't possibly survive this approach being standardized.
[0]https://www.youtube.com/watch?v=RLw13wLM5Ko