Not necessarily. Though I agree it's better they are as rare as they are. They might be just extremely natural nen users, with not a small touch of insanity making it work. Nen seems like something a genuinely insane person could boost to the absolute maximum, even if they they were rendered largely useless by the madness otherwise. Kind of like the image of an autistic person excelling at something beyond most, yet being otherwise a compromised person. In fact it's not so far from willingly setting a condition like Kurapica (and apparently Gon) did. In Alluka's case her ability to use the power is extremely limited as she can't even decide herself what it's used for but instead somebody random gets to make a wish.