If it takes too much effort for you to mew then you probably aren't suction mewing because suction mewing is a lot easier to do with an all-day effort
Since mewing is tongue posture and on the upper palate you don't necessarily need to mew to have a good lower jaw if that what you're reffering to - that is why I linked to the other thread to show how to result in lower jaw growth using the neck and head position combined that another user posted.
If you are referring to upper jaw size not being related to mewing I respectfully disagree -
in experiments with monkeys with healthy jaw growth and their nasal pasages were blocked with a substance causing them to mouth breath - their jaws suffered tremendously - I don't think the upper jaw magically maintains it's shape and size without anything holding in that position especially since breathing through the mouth harms this position.
This is why you see when most people "Get older" their jaws tend to shrink in general - I think if they don't maintain healthy tongue posture their jaws get smaller as nothing is there helping it maintain shape
they may not "know" about mewing but we can see with most animals in the wild avoid mouth-breathing and keep proper tongue posture and I highly doubt those animals watch YouTube videos on mewing as well
www.buteykobreathing.nz