Yes, everyone understands that. But tradeoffs that are acceptable for life-or-death questions are usually assumed to involve some human decision at some point. That's precisely what he's saying

Basically his argument is "we will still need mathematicians, because for some large classes of problems (one could argue, the most interesting ones, the "applied" ones) we still need to have a subjective human decisions of whether the machine solution is aligned with our values or not"