I agree but would propose the weaker argument: no set of human contributors have, put together, read and understood all the code. Even in artisanal-coded projects of sufficient size, it's rare that any one human has read and understood all of it.

The million or so lines of the original code has been "battle tested" for what it's worth.

This is a massive codebase created within a week or so ago, no one can say what it will do till it does.