Nandrolone gets 5-alpha reduced in your body to the much less androgenic dihydro-nandrolone.
Finasteride is supposed to stop that reduction and leave more androgenic nandrolone in your bloodstream.
I don't think you will find any real life evidence proving that nandrolone+finasteride is a hairkiller....just "bros" telling you that they have a "bro" who lost all of his hair stacking the two (aka bro-ology)
Just don't do it to stay safe.