Diana Conqueror bug

DIana only gets 3 stacks of Conqueror while hitting the enemy with 4 abilities/autoattacks.
In my video I hit the Training Dummy with Q, W orbs exploded on it, hit an AA and used R, expected result would've been 4 Conqueror stacks, however only 3 were awarded. Each individual ability does provide 1 stack and if you stagger it more you also got 4 stacks.