If we look at the Bill of Materials of BlueROV 2 they have written the thrusters separately as clockwise and anticlockwise. Why not use Reverse config. ESC instead of anticlockwise propellers?
As explained on their website:
The T200 comes with clockwise and counter-clockwise propellers to counter torque.
And when you look at the body of the vessel, you can see six thrusters distributed around it. Given that it's intended for work in confined spaces, I think that it makes sense that you would want the propulsion to be balanced.