The argument is that you need to completely resolve executing the maneuver before moving on to the next bit. You haven't completed resolution until you've competed all of the related triggers. Kanan is triggered by executing a white maneuver and needs to be resolved before moving on to the next, separate thing that the card instructs you to do.
A trigger would only be related if it said 'When you execute a maneuver'.
Kanan says 'after a friendly ship ... executes a maneuver.' So the maneuver clearly is completed. Otherwise Kanan can not trigger.
Edited by StephenEsven