Board Thread:Questions and Answers/@comment-6576725-20180211015533/@comment-6576725-20180212080357

It doesn't decrease Youpi's Nen though the way Knuckle's ability works is that the person he inflicts it with has to expend enough Nen energy for APR to go pop. I believe it was close to doing so before Knuckle was forced to call it off cause Youpi was threatening to kill Morel. So with an extra very powerful and capable fighter, that being Illumi, fighting Youpi and stalling for time. APR might soon activate.

Also one thing Shaiapouf did against Morel is use his Spiritual Massage to read Morel's emotions. Since Hisoka's are much more chaotic and bloodlust. He would have a hard time trying to play mind games with him like he did with Morel. Heck seeing Hisoka's emotions might freak him out a bit although he would probably say that it's not as different as Neferpitou's.