Lord El-Melloi II-sei no Jikenbo - Vol. 11 Ch. 53

[MangaDex]

 

[spectralSpices]

Faker? I thought it was Pretender...

 

[Umbrum]

Faker? I thought it was Pretender...

A joke? anyway this is just the way dr heartless decided to name it, in essence they seem pretty similar so I'd guess those two classes are equivalent.

 

[Reignsan]

Faker? I thought it was Pretender...

She's a Pretender in FGO, but in Case Files she was a Faker. They're pretty similar classes and I'm not entirely sure what the difference is, but Faker was made first since the novel released in 2016.

 

[flashmozzg]

She's a Pretender in FGO, but in Case Files she was a Faker. They're pretty similar classes and I'm not entirely sure what the difference is, but Faker was made first since the novel released in 2016.

It's addressed in her profile entries and voice lines.
I.e. her summoning line is literally:

I've come to answer your summons. My name is Hephaistíon...
Hey! What the hell!? Why do I remember everything!? You are...
Ohhh, okay. I get it.
Just put this down to the weirdness of my class.
I am Hephaistíon, or someone pretending to be them. My class is Pretender...
But if you don't mind, I'd rather you call me Faker.