John Mew is very vocally against hard mewing.  He always pushes very light action over a long period of time as his entire point is mild postural action and I too think this is optimal.  I am not sure where hard mewing originated but I am mostly against it because of the reasons you said.  Excess focus on the back of the tongue can even cause Vagus nerve dysfunction and keep the body in a overly stimulated/stressed state.  Lately, all i have been thinking about is mewing and fixing my face and pressing my tongue super hard against palate, pushing so much force, thinking about it every second, and its very unhealthy. This is not normal. People with good jaws aren't pressing abnormally hard

The back of the palate is very thin and porus and hence very modifiable, the issue arises with too much force back there relative to the front.  That can cause the CW rotation effect which is undesirable for many cases. 

I think we need to mew on front part of palate more than back. Because from what i have seen, pushing on the back of palate causes clockwise rotation of maxilla so therefore, pushing on front of palate should cause counterclockwise rotation which is what you want. I have also heard from people that got results that they focused more on front part... back part needs to be activated too but if it already is up, then no need to focus attention there. focus it on the front.

thats my theory.

I love what @ThaGangsta said:

"I see what you mean there is a subtly visible change.  The back part of the palate is very flexible and thin bone-wise so you definitely might see changes faster there as in your case.  "Hard mewing" with the posterior third of the tongue will lead to the clockwise rotation where your ramus will sit higher from overclosure of the mandible and because the front part of the maxilla has not kept up or exceeded the back part, it will sit lower.  In my view, focus more on the front part of the palate if you can and this should be done in a gentle postural way.  The use of upward force is a common mistake many people coming into this make and all it does its jam the maxilla up against the remainder of the bones, warps it in an undesirable manner, and creates all kinds of cranial strains.  Thank you for sharing your experience here.

This should be a cautionary warning against "hard mewing" for all, mewing is a postural position that you naturally take, not a resistance training exercise.  I can understand why many push hard, it is simply due to determination they have for changing their face, especially in today's world.  I encourage you to use that determination to instead make sure that your oral and body posture are optimal, instead of using force, as after all we are all only given one skull.  No amount of force will bring you faster results because the action of bone cells in adaptation with proper mewing is very slow.  You can push and pull as hard as you'd like but it simply won't help.  The goal is not to jam the maxilla against the skull by pushing hard on it, it is to gently change its shape and position with mild forces over a long period of time.  Hard forces will lead to strains, compensations, tooth intrusions, and internal thickening making it even harder to change.  You can definitely move bone with hard forces, but you won't change its shape into a more optimal one.  I understand that things like MSE use a lot of heavy forces, and they can be useful in certain cases, especially where there is a functional nasal airway concern that need a more immediate resolution.  

The only "hard" things in this process should be brief chewing (if you need to build up resting muscle tone and provided you don't have any TMJ symptoms), the intermittent force from swallowing which may help in the process, and your willpower to create change.  "