Sim, o PAM está preocupado com autenticação e autorização, mas não com identificação:
"... you should know that PAM does not handle identification. Systems that rely on PAM normally use Name Service Switch (NSS) to manage identification. NSS also [like PAM] originated with Solaris, and predates PAM by a few years. The lack of integration between NSS and PAM has caused a continuous migraine for Unix-like systems ever since."
"Pam Mastery", Michael Lucas, capítulo 0