WTAF - split throttles,
It's normal on a warship. Two propellers pushing at different speed turn the ship quickly making her more reactive in action. Turning with the rudder requires a lot more time.
The issue here seems to be that the helmsman(*) inadvertently activated a function meant to be used in combat, although the article doesn't explain why they were passing so close to the tanker and other details.
* Is the helmsman also controlling the speed?