I imagine that after 30 minutes of being inclined while using the keyboard/mouse, the reduced blood circulation in your hands and arms from gravitational resistance will cause them to be incredibly tired/ fatigued.
Agreed. If anything, the arms should be allowed to stay horizontal, elbows leaning on the armrests and keyboard/mouse placed almost on my lap. With the eyes looking at the screen, it would be suitable for the touch-typing folks.