Probably because thats how most companies do it because most corporate workers are lazy box-tickers who are long fed up with the processes. It really feels like we're forcing human processes onto AI.
What actually is the point of TDD? - If its to force you to think about edge cases early before you've started building the feature then that sounds like a human trait - If its to be living documentation then that sounds like a human trait
We're going into weird rabbit holes where we've mismatched the tool that is AI which produces extremely cheap code very quickly - with the processes that we've built for slow and expensive to write human-generated code.
I think most people miss the point of TDD. It is not just about edge cases. It ought to be:
* A way of matching requirement use cases to tests.
* to modulate the number of tests written not only to make sure you have enough coverage but also to make sure you don't pointlessly cover the same edge cases multiple times.
* a way to cheaply provide feedback and validation on code as you are writing it.
With AI the ability to churn out useless tests has exploded (both with TDD done badly and with no TDD at all) and that has actually incurred a new type of cost we didnt have to face before.