It wouldn't really be that roundabout, he writes Hisoka's and looks for lines regarding winning or losing a big long sought battle, when the poem says he'll lose Chrollo let's Hisoka catch him expecting to win based on Hisoka's poem.I thought the same thing when posting a reply to Twisted, that Chrollo could've simply predicted Hisoka's future and know his own through that. However, it's a really roundabout way and he could die by other means so I don't know if Chrollo would go out of his way to do that. If he did he must've really seen Hisoka as a threat. I just don't think he would go that far.