The optics was fine and the sound bites heartening.

Democratic People's Republic of Korea leader Kim Jong-un and Republic of Korea President Moon Jae-in delivered exactly what they were expected to.

They announced a key document on eliminating mutual military threat, a substantial follow-up to the historic April 27 joint declaration vowing to stop all kinds of hostile acts.

They proposed to jointly host the 2032 Summer Olympic Games.

And they reached an agreement on Kim visiting the ROK, along with other measures to broaden and deepen constructive engagement.

The most significant part of Wednesday's joint declaration to other stakeholders, though, is its Article V, which vows to "turn the Peninsula into a land of peace free of nuclear weapons and nuclear threats, and for that purpose make substantial progress as soon as possible".

To substantiate Pyongyang's sincerity, the document does go one step further, offering to "permanently deactivate and abandon" another key engine test and missile launcher facility. Aside from that unilateral, unconditional offer, it also highlights "additional measures" like permanently discarding nuclear facilities at Yongbyon, on condition that Washington "takes corresponding measures".

The third Kim-Moon summit was more like a bifurcation than a turning point. Although US President Donald Trump has welcomed the development and indicated negotiations with Pyongyang may get back on track, anything can happen moving forward.

But the Kim-Moon summit in Pyongyang did indicate one thing: inter-Korean rapport may develop faster, with the denuclearization process moving in tandem but on a slower track. Not that thawing Pyongyang-Seoul ties does not help denuclearization. They are a precondition for the latter. Yet they do not suffice for the latter to materialize.

Clause II, Article V of the Pyongyang joint declaration reiterates the DPRK's already clear position that the ball is now in the US' court, and the prospect of denuclearization is contingent on the latter's response.

If Washington insists suspending some high-profile exercises alone is a qualified response and show of goodwill, substantial progress may be difficult to achieve for the time being.

Although the new joint declaration does not clarify what constitutes "corresponding measures", it does hint at something better. In earlier appeals to Washington, Pyongyang had asked for formal termination of the Korean War, the state of war to be more precise.

Considering the symbolic nature of the lingering state of war on the Korean Peninsula, as well as the substantial moves Pyongyang is to make in return, Washington ought to give it a serious thought.

In the mean time, Seoul may want to push both parties harder to achieve greater progress on denuclearization, because inter-Korean rapport cannot go too far without addressing such a broader international concern.