Hmmm... so in the case of a "dog collar", Adobe would we consider "dog" to be an adjective? Interesting... I never thought about it like that, but I guess that makes sense. Still, they need to work on their definitions.
Grammatically this is known as apposition, where you have two nouns (or noun phrases) next to each other and modifying each other. In English appositives aren't considered adjectives, but they do behave similarly.