They launch them on a nearly vertical trajectory to test the range vs a more horizontal course which may draw return fire.
Our return fire wouldn’t be inert test rounds, but most likely the contents of a boomer sub.
Exactly right. If NK were to launch something on a long range trajectory... Our satellites, radars, and computers are very good at determining impact points. If NK were to make a mistake (what are the chances, ha!) and their test shot was going to impact on the west coast.... Are you going to believe their frantic call that it is a mistake, that it is inert? Of course not. We’re going to shoot it down. Since interceptors are limited, we can’t afford to keep shooting them, so an integral part of defense is counterstrike. We would respond in kind , with WMDs, taking out at least that launch site, possibly several others. So NK is at least marginally smart by not shooting long range, risking an accident and nuclear destruction.