Ninja is not Thief, it is Ninja. The UI will say it is Ninja, the lore will say they are ninjas, you will be invited to parties as a Ninja, and you will perform Ninjutsu.

This is not what I wanted when I wanted Thief to be included. The notion that there may not be a Thief class annoys me. That people justify it class play with 2 nerfable turns of coil and PVP infuriate me.