The Samsung JU6400 still uses a VA-type panel.
I also observed the same thing about the better rigidity (I don't know if this is the right word to use, but it suffices for now) of Samsung's newer VA panels which came out last year.
But IPS panels, especially those made by LG, still feel harder or more rigid to me when I soft-knock on the screens.
I have the JU6600, also a VA-type panel, delivered to me recently but I have not unboxed this puppy yet.