You missed that?
His statement here is annoying, but it is also a non issue. Presidents are always personally tied to their foreign policies, and their opponents always cast it in a negative light. So what if he digs into Trump a little.
The rest of what he writes is reasonable. North Korea is at least agreeing to allow some inspectors and dismantle facilities. At the same time, reunification could derail everything. That problem would still exist no matter who was President.
The only difference is, the news would rather have a Democrat taking the credit. Unless I missed something.