Removing the whole title bar implies no window buttons, the point is having them while not wasting space.
As I already shown to you GTK apps display window controls according to a global config. So you can turn a header bar in just a toolbar. I don't know about other CSD apps but it would be their fault, not a CSD disadvantage.
It was another person.
Again, you are confusing the concept of CSD with GTK's implementation of CSD.
I give up, cheers.