Do whatever Airbus or your company SOPs tell you to do in the cockpit preparation documents. You should have copies of both documents available from your type rating and line training. (I no longer have access myself). If a Captain says to do otherwise, you can point out the SOPs to them. (Captains are allowed to vary SOPs in an emergency).
Generally though, only switch one thing at a time - especially in flight, (but I assume this was on the ground). Switching each battery off then on forces each battery controller to measure its own battery and initiate a charge sequence if required.
If you switch all three batteries off and on simultaneously and there is a bang, or smoke, or everything goes dark; which battery or switch caused the problem ?
If pilots do not have time to switch things individually, they need to make more time. There should be plenty of time available to prepare an A330, because there are many more passengers to board, which takes longer to do than on an A320.