Trump has certainly made things unpredictable. We don't know if he is going to nuke the Korean peninsula in a first strike. I'd say that's pretty unpredictable.
As a matter of strategy, though, predictability is a tricky thing. When fighting in an asymmetric conflict, one side needs to be unpredictable. Against a stronger opponent, if the stronger opponent can see what you are doing, you are toast. You need to use stealth, trickery, etc. On the other hand, if you are the bigger, stronger opponent who can crush anyone in a straight-up fight, predictability is actually your friend. Your goal is to institute a deterrent. Make it clear that if someone fucks with you, you will destroy them, but if they steer clear, you will let them be. You need to set clear boundaries, and leave no doubt in your adversaries' minds about what will happen. See: Schelling, Thomas.
Of course, that's not really what Trump was addressing in the clip above. He was addressing uncertainty over tactics. Lately, Trump has tried to leave clarity in the minds of the North Koreans that he will destroy them with "fire and fury" (or was that not "tough" enough?) if they don't back down. What tactics will he use? Despite claiming to be "locked and loaded," he hasn't deployed any troops to the region. On short notice, he could launch air strikes, but really, his best short-notice option would be to nuke them. So, by not preparing any better alternative for a short-notice military option, Trump has left clarity on what he would do if he did act on short notice. The primary uncertainty, then, is if he really will press that button.
That's not actually how strategy is supposed to work. Not even by Trump's own contentions.