I never saw it as a real 'model', just a way of clarifying definitions, and making statements such as "I believe that {anything not a matter of fact}" null. It provides a way to distinguish between "I don't believe in invisible dragons in my basement." and "I don't believe in {immoral action}". I suspect the original intention was to validate a philosopher who got fed up with someone who hid behind 'I don't believe in that' in a discussion, after which the philosopher responded with evidence that the subject under discussion was factual.