That proves AI is capable of doing one part of the software engineering process. The 16 devs in the study trusted AI to write the code. Once we trust AI to do the verification as well we'll realise the gains we feel we're getting now. Essentially we're intentionally going slower on the second half because the trust is missing.

Alternatively, rather than trusting AI to do the validation, we could follow the vibe-coder approach by skipping the validation entirely, and trust that the generation stage is good enough not to need it. Historically that's come with some small downsides, like the code being a broken mess of security holes, but with time AI might fix that.