Milord I mean, everything we do in life is a tradeoff of risks and benefits, and we constantly set acceptable risk levels. If we always played everything safe, we would get nothing done.
That said, not having an emergency key is a lot of risk for very little reward. Sure, the belt will feel mildly more secure and there is mildly less strain on your willpower compared to a sealed emergency key, but belts are not indestructible nor inescapable (lockpicking is a thing, and neither small padlocks nor most tubular locks are particularly resistant against it), so there is already some level of trust that the locked person will not act out of line involved in belting.
And yes, in everyone's favorite horror scenario of several broken bones and whiplash after a traffic accident, the key is probably not going to make much of a difference. But there are plenty of other emergencies that might require immediate release without rendering the wearer unconscious or otherwise unresponsive. Inflammations would be the first thing coming to my mind.
If you have carefully assessed the safety implications of not having an emergency key, I could somewhat accept (but not condone) the decision you made. You are your own person and you have the right to make reckless decisions. But when it comes to a keyholder forcing such a decision on a wearer, this sort of distrust is a massive red flag. When it comes to recommending unsafe actions to beginners, you are putting people who are not equipped to make that assessment themselves in harm's way. No. Just no.
