I see why you're saying that, but I think you missed their point. Challenge trials might well allow us to make a safe vaccine available sooner to those who want it, but if we mandate a vaccine that has only undergone challenge trials and then that vaccine kills someone, it would certainly be politically disastrous for challenge trials.
In a normal trial, you give half of participants a vaccine, and half of participants a placebo. Then, you wait around and see how many people in each group catch COVID naturally and get sick. Your vaccine works if fewer people who received a vaccine get sick compared to the placebo.
In a challenge trial, you give half of participants a vaccine and half of participants a placebo, and then purposefully expose them all to COVID so you don’t have to wait around for them to catch the virus naturally. As before, your vaccine works if fewer people who received a vaccine get sick.
A challenge trial gives you data which is more, not less, robust, because you’re controlling for more variables between groups. And we’ve used challenge trials to test vaccines in the past—just, never with a disease that’s nearly as deadly as COVID.
Any firestorm would result from a trial participant dying from the COVID they were purposefully given (which could absolutely happen), not from the vaccine. This has nothing to do with vaccine mandates.
Challenge trials have nothing to do with adverse side effects in the original clinical safety trial. We also have good proxies for challenge trials for COVID.