פירוש על קידושין 97:6

In the next mishnah, we learn of cases where a husband lies about his lineage. Even if he says that he was a Levite and it turns out he is a priest, a more prestigious lineage, she is not betrothed. R. Shimon does not disagree in this case. From here we can conclude that he only disagrees if the deception was with money. If the deception was with lineage, i.e. he has better lineage than he stated, she is not betrothed.
A “natin” is a category similar to a mamzer, both of whom have very limited marital prospects.