It is mostly symbolic. Should the North have decided to go South, all those guard posts could have done is die in place. The sensors that were doing the real work are still in place and monitored; the rapid reaction forces that would have avenged those dead troops is still there - and this says nothing about the thousands and thousands of Samsung SGR-1 sentry bots/drones monitoring the border.
Along with the 26 miles in depth roadway rockslide/avalanche barriers and 1000 foot hillsides in rows to Seoul, the border is secure from your basic land invasion to the capital. Some rumor 26 nuclear bombs buried in the South at the DMZ to cause further damage to Northern Invasion routes.... That rumor has it basis in the joint Taipei-Seoul, Pretoria-Tel Aviv nuclear development project in the late 70’s, a time when the Soviet-led UN kept these four unlikely allies out of the UN official body.