A standstill ship with two propellers and two rudders (but only one rudder control, like cost guard cutter and Vigo) when putting port engine ahead and starboard backward the ship is turning clockwise. Normally if you give full rudder port, then the port propeller wash is deflected to the port and push the stern towards starboard, countering the rotational movement. If the throttles and rudder angle is adjusted correctly you would get the ship to move parallel, also called walking. This is not what happens with the ships I tried. This is a really important technique and is common to control rotation of the ship during low speeds, especially if you lack bow or/and stern thruster.
I suspect that there is a bug with regards to the propeller wash from the reversing side is also deflected to the opposite side, since both rudders are moved, hence canceling the sideway force generated from the side going forward. For the ship Vigo I can see that the propeller wash for the engine in reverse is changing with the rudder. For all ships with fixed propellers, the rudder should have no effect on the direction of the propeller wash in reverse.
kind Regards