Some rumors floating around that Marek leaked some draft pick info to colleagues who then leaked it to team(s)? When I attended the 2017 Draft, I was seated behind the NBCSN production crew and I could see them prepping up highlight packages before the teams took the podium. Before we made our pick, I was standing up with Hischier and Patrick nameplates. One of the production people turned around and told me it was going to be Nico (he'd later tell me that he wanted to help me get on camera).
As I understand it, the teams enter the pick at the table and then wait for the green light from the TV people to go on stage. I remember seeing the cameras at the 2015 Draft and each one had a big cheat sheet with photos of each prospect, so basically that's how they're ready with the reaction shot even for somebody unexpected like Beckett Sennecke this year or Mark Visentin in 2010.
In Marek's case, he was probably given the notice on the pick so he could prep for a couple minutes for the eventual interview.