No, the statement is perfectly sensible.
But. Somehow, i'd imagine China would step in if the NK were serious (ie not just rhetoric) about an attack to the US.
The reason is simple: US retaliation could draw China in a war in any case in some for, and if China were to take over NK, they might be able to keep NK as a strategic buffer in some form, which is the reason for current status quo. At least by acting preemptively they'd have better chance at that than after the US is there.
Ultimately, i don't think NK will really ever attack with nukes, for the current regime will lose its power in the aftermath no matter what (China takeover, US takeover, nuclear obliteration).
EDIT Actually, this is too optimistic. Depending on the situation in NK, they might just decide to go out in blaze of nuclear fire.