Terrence Tao is obviously extremely smart but he also clearly doesn't know anything about drug development.
This is literally how it works now.
The mechanism of action of many drugs, including chemotherapy drugs, are poorly understood.
We don't even know how Tylenol works!
Additionally all these drugs have tons of off-target side effects. In a sense most drugs are "misaligned"!
This is a slide from Terence Tao's 'Math 2.0' public lecture yesterday evening at Caltech. I am highly confident that, if the cure actually worked, almost any Stage 4 cancer patient would tell you that human comprehension of its mechanism is completely irrelevant to them.