While the assumptions built into the calculation are hardly to be considered hard data, the basic trade-off is true. Do we risk smaller casualties now by striking first (and soon) or risk many more casualties later when we don't have the same chance of winning in the hope that time will solve the problem?
This is basically correct:
Choosing to deter North Korea is to engage in a gamble: you avoid the costs of a preventive war today when North Korea is relatively weak, but you run the risk of an accidental nuclear war later when North Korea is vastly more powerful. Using plausible estimates of the probability of accidental nuclear war derived from the U.S.-Soviet experience during the Cold War, I find that gambling on deterrence will lead to 7.5 million U.S.-South Korean-Japanese deaths on average (under optimistic assumptions) while a preventive war now will lead to 1.4 million deaths (under pessimistic assumptions).
But I wouldn't call it "reckless" to choose deterrence. Although the lack of North Korean ability to detect an American attack does greatly increase the chance that North Korea will adopt a policy of "launch on warning" (of a preemptive attack) even if North Korea has no real way to be sure their warning is of an actual attack.
Over time that factor does approach "reckless" and may reach that stage, I admit.
And one factor is not even addressed in this calculation: Iran.
Iran is North Korea's partner in nuclear missile development and if North Korea gets nukes, Iran will soon have them, too.
Can Iran under religious nutball rule even be deterred, with accidental launch not a significant additional risk for nuclear launch at all?
(And even if Iran can be deterred from using nukes, their nukes will deter us from stopping Iran from doing more than they already do to wreak havoc in the region without nukes!)
That Iran-North Korea linkage my concern. I've long said that deterring North Korea can only be debated if Iran is not a potential customer--either by regime change in Iran or some as-yet unknown means of virtually guaranteeing that Iran can't ship the technology or actual missiles to Iran.
This type of analysis--as rough as it is--is the kind of analysis we need to perform after my concern is addressed and we are dealing with North Korea in isolation.
As an added factor, remember that while both action and inaction have consequences, politicians consider it safer to have consequences based on inaction, which they can more easily deny had any relation to the consequences--which might not even happen until many years down the line when they are safely retired polishing their Nobel Peace Prize.