The mechanics to justify moving the vertical (radial) force, V, to the inside diameter of the tube is two fold. First, the tube is trapped between the fluid and the reinforcement. The fluid pushes radially outward, and the reinforcement pushes back with equal force. Second, the lay of the reinforcement moves to the neutral angle.
The Evans solution for the direction of the neutral angle as 54° 44´ has been verified by decades of experience. Experience also tells us that the braid will move toward the neutral angle unless it is somehow blocked.
This is because if the horizontal force is greater than the vertical force, the hose reinforcement will elongate until the horizontal and vertical forces are equal. That only happens when the reinforcement braid angle is 54° 44´. The reverse is also true: if the horizontal force is less than the vertical force, the hose reinforcement will shrink until it reaches the neutral angle. This is why hose swells and shortens when pressurized.
To explain, we know from experience that when under pressure, the reinforcement always aligns at the neutral angle. So where does the vertical force act? It must be adjacent to the horizontal force so that the resulting force created by the vector sum of the horizontal and vertical forces lies at the neutral angle.