about Moira......

So I'm currently rewatching Murder House and I remembered one thing that never made sense to me. When people die in the house and become ghosts die they stay looking the same way forever, like they don't age. Well, Moira died when she was young, so why is her "true" form old? Isn't she supposed to stay young forever? I know that men see her as her young self, but she says several times that it's not her true form, so I'm confused. It doesn't make sense for Moira to age.

https://preview.redd.it/g75qbi5p2dke1.png?width=747&format=png&auto=webp&s=187f825872f4343a2171f346d1a87909094fa5af