It's done in training mode with meter set to full and the UI off. Note the lack of the 'end of round' animation. In MMH's trailer, you can even see MMH meter burn one of his specials directly before his super. NRS obviously has better tools for recording, so they can prompt the ending animation when they want the trailer to end. I'd bet it's pre-scripted, also - they are trying to sell you the character, so they need show the characters specials/throw/clash/super. Just having two people fight and hoping that it fits those criteria and ends up showing the character in a positive light would be pretty inefficient.
Honestly, I'm betting it is timed. The animation for the hat has Zatanna jump back a little bit, implying it wasn't Zatanna's doing. Why it's timed is beyond me, but we will find out during the stream on Monday. Either that, or they quickly switched back because a minute of Zatanna zoning would be incredibly boring.