No, the optimizer knows it's a view. However, it treats a view like what it is, a query. So while the optimizer understands that it's working with an object, the definition of that object is such that it gets treated as if it wasn't anything special (because, except for materialized views, it isn't).

However, don't take this as criticism. You're dead on accurate. It's not the view that's making something slower or faster. It's something about the query against the view vs. the other query and what the optimizer can do with it that is defining performance here.