Amnesiac remembering dead unique role

[Deantwo]

there can only be one Mayor or Marshall is a game.
there can only be one Godfather in a game (with the expiation of Consigliere replacing the Godfather apron his death).
there can only be one Mason Leader in a time (with the expiation of other Masons replacing him if the correct options are enabled).
there can only be one Witch Doctor in a game.

Amnesiac can not remember being someone that there can only be one of.

it also make sense that there can only be one Mayor... and if the Mayor is dead... how should you have been him? at least if you think of the Amnesiac as having always been he's target... he just didn't know it till he remember ^^

EDIT: i guess Cryptonic gave the reason as to why it's like that game wise XD