I'm not a metaphilosopher, so my response is based on An Introduction to Metaphilosophy (GB) by Overgaard et al. (the Authors). The question strikes me as analogous to the question of what constitutes a scientific theory, the demarcation problem. I'm going to attempt to describe the Authors' analysis as a response to suggest an answer to the question.
First and foremost, metaphilosophers are obviously interested in answering the question 'What is philosophy?', and their method is comparative. "Chapter 2: What is philosophy?" conducts a survey to establish a taxonomy of approaches to answering the question. In doing so, they are answer "What is philosophy?" as descriptivists and not prescriptivists and in this regard are taking an empirical approach to philosophy. So we can say with certainty that metaphilosophy handles non-professional philosophers (NPPs) as an empirical reality.
Reading the chapter, however, one sees that the chapter is not organized by individuals, but rather by types of metaphilosophical theories. So, if NPPs are treated as an empirical reality and taken seriously as contributors, the Authors are included in the taxonomy based on their claims. While they don't say it, I think implicit in their categorization is to admit the principle that a person should be categorized on the basis of their philosophical thought, not their credentials. That being said, I don't see any NPPs referenced in the chapter at all. It's the heavyweights such as Plato, Ryle, Carnap, Quine, Wittgenstein, as well as more contemporaneously recognized thinkers such as Hacker and McGinn.
So, the next place to visit the Authors' assessment is the bibliography. Again, it's a who's who of philosophers, but few NPPs. Richard Feynman and Thomas Kuhn are included (the former a physicist and later a historian by education), but the list looks rather bereft of even big names that are normally thrown in discourse such as Hawking, Penrose, Harris, and Chomsky. I think we can take this as a sign that metaphilosophers as a practical matter acknowledge that many NPPs lack the formal education to speak authoritatively on metaphilosophical matters (in contradistinction to metaphysical matters). Sure, Chomsky can more than hold his own in a debate about philosophy of language (he did revolutionize it) and philosophy of mind, but he may not have the expertise to compare and contrast 2,500 years of philosophical literature, especially given his preoccupations with political philosophy.
So, I think it's fair to say that philosophers in general brush off "intrusitve" pronouncements about philosophy (I always use Bill Nye sticking his foot in his mouth as a short-hand for these "intrusions") because they're so poorly constructed and ignorant of philosophy, that metaphilosophers, who make a practice of evaluating philosophers, especially the world's greatest, consider such "intrusions" a minor feature of their theorization. But then, I'm not a metaphilosopher and am drawing conclusions based on a single volume (which as far as I can tell seems to be the authoritative work given the recent emergence of the discipline).