Not sure I agree with the "Any time you deem right" section. You make a move as an MC whenever there's a lull in the conversation or everybody looks to you to say something which already gives you plenty of options to influence the story.
The example given is to "introduce the villian’s [sic] new sidekick/horrible weapon/escape plan immediately as the player’s move resolves, without waiting for a failed roll" if it looks like they might defeat your villain too early. This doesn't really seem to be looking at everything though crosshairs and flies in the face of always give the players what they work towards. It's probably something else new MCs miss a lot - that while you never roll any dice and your moves are all very open-ended you can absolutely still cheat, which isn't fair to your players.
The correct thing to do in a situation where they're killing your villain "too early" is to let them, but put your bloody fingerprints all over it. Have the villain's daughter run up to the body and start crying and hugging it. Skip forward in time a few days to when refugees from the villain's hardhold are showing up demanding food and water, since you killed the guy who was providing them with it up until now. Have the bigger, badder chick from out across the burn flats show up, moving into the power vacuum that was left. None of this fails to make your players life not boring but also none of it denies them what they worked towards.
What you should never do is have the villain survive just because you like them, especially when the players are involved (if it's between NPCs, sure - having them show how badass they are is fine, but they're never more badass than the players). I did that for the first game I ran, had one of the Solace's "Wolves of the Maelstrom" be a young girl called Grandma who'd taken over an army base and filled it with obedient soldiers using her ability to command people to do what she wanted straight into their brains; awesome character but she nearly ruined the story, because all the players kept being like "Oh, well I want to go do this awesome thing, but if I do then Grandma will have me killed."
Sorry if I seem overly critical, the rest of the article is fantastic; just that last point that seems exactly the opposite of what PbtA games are supposed to be. If you meant something else, then let me know, but if that's the case then it could do with wording better so nobody interprets it the same way I did.