Construct is about picking on the left and applying actions to those picked on the right. You didn't pick any BrownBox so it applies the animation to all. BrownBotBox is a different object so they don't relate. The reason it falls off screen correctly is because you picked the BrownBotBox on the left (on collision with) so it disables the collision for that one only.
With this particular event you could add a condition 'BrownBox is overlapping BrownBotBox', this would correctly pick the one you want to set the animation.
There is also something called a 'Container', if you put BrownBox and BrownBotBox in a container then they would relate in events, this avoids picking but it's also good to be aware of picking as described above.