Do you have a source explaining why NPD is neurodivergent? My understanding is that autism is a neurodevelopmental disorder with a significant genetic component that, depending on severity, can seriously disable independent life. On the other hand, npd is never a disability, it is supposed to have something to do with early childhood experiences. It is a (somewhat outdated) psychological description of the way how the personality of otherwise biologically healthy people can be like and has little to no genetic predisposition.
My opinion: caring for a dependent who is autistic can be really hard, but it’s something someone does for a loved one. Being around a narcissist sucks and the only options are to set hard boundaries or get them out of your life.
Of course that distinction only matters if you use the terms to describe the disorders they mean, not if you just call people who are awkward with others autistic and people who act self centered narcissistic.