>>283573119
That's literally the only thing they DON'T know.
Rom and Ezzo have already figured out that Al is a time-looper, and they also know that he has strict limits to how far he can go, but they don't know what the trigger is to activate his Authority, if such a trigger even exists.
Petra and Oniricbaru think that Al's domain may work the same way as Return by Death, but we have no explicit confirmation of Petra telling the group about such a possibility.
>>283573292
Rom was sure that Aldebaran's Authority worked by setting savepoints, so he analyzed every time he changed his course of action to predict when he would autosave.
He had no idea what the trigger for Al's Authority was, but he knew that he wouldn't be able to go back to his previous savepoint to escape his suicide attack and tried to put him in a situation in which he would die 100% of the time to force him to give up and die
