[aethr]

You're right, when talking about a primitive type in the programming sense, something either is primitive or it isn't.

I took this phrase to mean that the prototype construct is "one step down on the composite type hierarchy" from what is needed to emulate as a Java-style class.

Rather, its a good building block but the necessary boilerplate code makes it "too basic" for that purpose. Therefor this developer has created a type further up the composite type hierarchy (or further away from the primitives) to accomplish his goal.

I don't think he's trying to suggest any deficiency in the expressiveness or capability of the prototype construct (he's obviously quite familiar with it to create this language). This is simply a tool for people who aren't familiar with (or don't make use of) that aspect of Javascript to be productive by utilising a more brief, or possibly more familiar (ie Java) syntax.