Why could Ymir read the can, but Reiner could not? While watching episode 29, we saw that Ymir could read the letters on the can, but Reiner could not. Why?

Manga spoiler:


   As far as I remember, both Ymir and Reiner are Eldians. So should they not both be able to read the letters on the can? What language is supposed to be on it? Why can Ymir read it, but Reiner could not?
After some researches on the wiki, i found something interesting :


  Even if they both are Eldians, Ymir was part of the cult of Ymir (It's also the reason why she was condamned to be changed into a titan). It could be there she learned the language on the can, and this language is probably linked to Ymir Fritz herself. However it is pure speculation since we have no way to really know.


Source : Chapter 89 (p. 8-13), Eren is reading Ymir's letter which tells us about her past.