A lot more bad logic will get by the smell test when you have 1 staff member vibe-coding. And just wait until he is held to that level of zero-test, lowest hanging fruit productivity as being "normal".
That is a good point that wasn't in the original description. I do think test engineers will become more important to ensure the generated code actually fits the requirements. We might even see the role evolving towards more of a business analyst role using LLMs to generate the tests and then adjusting/validating them based on the requirements.