Max Fisher suggests that the B-2 runs from the air base in Missouri to the Yellow Sea, and even more the way in which they were publicly announced, had as an audience not so much North Korea as South Korea, where there have been grumblings on the right about developing an indigenous nuclear capacity. The B-2 runs are a way of reassuring South Koreans that the U.S. has their back.
Notice what Fisher does not mention: the U.S. soldiers on the ground in South Korea. They are not part of this particular story. Nor are any bases in South Korea part of this story. The B-2s took off from Missouri, flew to the Yellow Sea, dropped their inert munitions, flew back to Missouri. Sure, the point was to send a message (one can debate about who the intended recipient was), but the exercise is also an example of offshore balancing. Or rather, it's the sort of thing that would probably become more frequent if the U.S. adopted an offshore balancing approach.
Also (and unrelated), Fisher comments on Der Spiegel's interview with the head of Mali's military government: here.