Then what was your splendid reason? The other Phantom Troupe member, who is a master of nen use as well, needs to go through Hisoka's fight in excruciating detail as if it was something novel to her? She fricking knew everything that happened from the beginning, so why on Earth was it necessary to make it look like she thought it all through in Hisoka's company? It's poor story telling, that's all. It's as if the audience was sitting in that same room, listening to a lecture, and not a meeting of Hisoka and Machi alone. It made about as much sense as the infuriating studio laughter that ruins sitcoms. But unfortunately it's still a part of the shounen textbook.
A better way would have been to leave the explanations to later, until Gon and Killua need to figure it out. That way, when they are still struggling to get it, it would feel natural to explain it to the audience as well.