Only considering the height is not enough. Many pannier setups will place the load quite a way from the center line of the bike and a long way from the rider and the ground contact patch and so it's not as easy for the rider to correct unbalanced forces that might occur. Of course the stability and slow response that such a setup produces has long been seen as either an advantage or a necessary evil. With a saddlebag the correction only requires a subtle shift from the rider. Of course if the saddlebag weights 50lbs and the rider is 100lbs the correction would need to be far from subtle. I'm not saying a saddlebag set up is more stable than one using panniers, just that it changes the handling of the bike less.
I brought up bikepacking saddlebags as a point of comparison because they are also mounted to the saddle and might be more familiar to the community.
Yes it does. The reason why MotoGP bikes have gas tank between the seat and engine.
Stop making excuses. And your false claim with panniers makes things worse than a saddlebag.