Chosun-Ilbo is as close to an official government news source as it gets. Think of them as the South Korean equivalent of Sean Hannity. If they said that this caught the South Korean government and military by surprise then it's clear they had no idea Trump was going to do this.
If it matches the US lamestream media meme that “ Trump just threw our allies under the bus’” ‘then I’m taking it as fake news
Pompeo laid a lot of the groundwork for this summit - he wouldnt play that game nor would Trump
Those South Koreans that are highly involved - aren’t talking or complaining they were surprised by anything that happened