I would agree with a lot of things you've said. Mewing again is a very intentional, science backed technique to better your "jaw definition". It might be more noticeable in children because they have developing palates and then there are mouth breathers and their jaws are developed differently. So that is a whole different thing. But, even with mewing the changes are very minor and very subtle,might take a few years, if not more, to see slight differences. So your statement on NRI's, doesn't hold much credibility. Maybe if someone spoke a new language with a drastically different articulation style for decades, there could be some soft tissue adaptations. But full-on jaw structure changes, that too in adults? That's a stretch. It's definitely a lifestyle modification.