It should be ok, if you teach them all forms of object creation. They must know of .__proto__ and .prototype. Make clear that the class keyword generates a function and not a class in sense of C++/C#/Java/... .
You never use it direct. But it is the reference to the prototype. So if you use Object.create() or Object.setPrototypeOf() you working with __proto__.
But you are right. It's only background knowledge.