Ninja is a variant class of Rogue rather than a completely separate class of its own, so rogue level and ninja level are the same thing.
So, does that apply to ANY class that gets access to Rogue talents?
Stalker gets a Rogue Talent and uses that Rogue Talent to get a Ninja Trick...Stalker levels are considered as Ninja levels for talent?
Sometimes you have to just use common sense: any time a feature is given to you by a class from another class source, and that features references that different class level, you can substitute the class that gave you the borrowed feature in the rules text.
What AwesomenessDog said.
It's not actually written down, but whenever a class feature grants access to class features from another class, unless otherwise specified, all instances of the class name are relaced by the name of the class that granted you the option to begin with, or "the character", as appropriate. This is evident in stuff like the Exploiter Wizard, because every single Arcanist Exploit talks about "the arcanist", if the above wasn't true, the archetype couldn't use any exploits at all. it's not just archetypes - almost all rage powers state their effects for "<the/a> barbarian", if you couldn't ignore that on another class, the Skald class's signature class feature wouldn't work!