This article sent to me via a reader tip is a couple of months old, but it is yet another example of what the Moon administration really want to do with the US-ROK alliance even though officially they will say something different:
A top adviser to South Korea’s president says he would eventually like to see the U.S.–South Korea alliance end. In language that sounded almost Trump-like, Chung In Moon, a special adviser to President Moon Jae In for foreign affairs and national security, said in an interview that alliances in general are a “very unnatural state of international relations” and said that, “for me, the best thing is to really get rid of alliance.” In the meantime, he says, he “strongly” supports “the continued presence of American forces” in Korea, despite hoping for an arrangement that he thinks would better serve his nation’s interests.
It was a remarkable statement coming from a South Korean official who is playing a prominent advisory role in current negotiations over North Korea’s nuclear program. South Korea has relied on its U.S. alliance since the 1950s to deter threats from its north—and the fate of that partnership, which North Korea has long sought to end, has been a contentious question as a summit between Kim Jong Un and Donald Trump approaches. U.S. and South Korean officials have repeatedly insisted that the alliance is not a bargaining chip with North Korea. And Moon, who presented his ideas as his personal views, was discussing the future of the alliance as a theoretical question about Asia’s security architecture, not as a matter to be determined in nuclear talks. But his comments nevertheless suggested that if those talks succeed and overhaul geopolitics on the Korean peninsula, the alliance could come due for a reckoning. [The Atlantic]
You can read much more at the link, but President Moon is a very skilled politician that needs to keep the Korean right at bay and public anxiety down. If he advocated openly for a USFK withdrawal that would give the South Korean right an issue to strongly attack him with and cause much public anxiety after decades of security guarantees provided by US forces.
However, if a peace treaty is signed to end the Korean War do not be surprised if the Moon administration allows left wing groups begin to put pressure on the US to withdraw. Think of it as a macro version of the current THAAD issue. The left wing groups have protested and sealed off the THAAD site making life difficult for the soldiers there. The Korean government could easily end the blockade, but choose not to. What if in the future if these groups are allowed to blockade and make life difficult for US personnel at for example Camp Humphreys?
President Moon will say all the right things that he supports USFK, just like he supposedly supports the THAAD site, but will set conditions to make it difficult for its continued existence.