You have to remember that humans generalize by default. It's the foundation of our entire social structure after all. Terms like "Nintendo games", "cinematic games", "indie games" or "mature games" are usually said in reference to specific common traits or themes.
For example, the majority of Nintendo's major IPs are cartoony/family friendly games with little focus on story, and many also share the same characters. There are exception, and the games themselves may span several genres, but that core theme remains consistent enough for people to make the generalization.
The generalizations themselves are somewhat small minded, but they're often useful for simplify conversations. Their use is also backed by how many commonly people generalize their own tastes (in part because we enforce our own biases), such as "I dislike [Sony/Nintendo/MS] games".
