No idea but auditing code is common practice in most tech industries (it is a boring job) as it is like looking for spelling mistakes in a text. The testing I did was localisation for languages and it doubled as test service that ran specific test cases to look for errors.
Here, it might not even have to be as formal but I wonder how many witnesses fully audited it considering it had so many massive issues and then, in a couple weeks, how much of the testnet could be thoroughly tested. From my limited understanding, there is a fair bit of complexity and a lot of things that can easily be overlooked so, having fresh 'less' biased eyes limits risk a bit further.
Yeah, I hear you. I've heard many witnesses suggest they don't even try to audit the code. It is frightening. :)