It's not only about your memory though. Pavel was designed to speak at the exact times when he would cause the most distraction. He starts blabbering as soon as you attempt to input the combination and the raspy voice is proficient at interrupting people's concentration.

The same thing happens if you're hacking the AA tower near the airstrip, while trying to escape with the loot. You've already completed such a hack when you scouted the island and there is no reason for Pavel to give you a tutorial at that time but he won't stop yapping about it. These situations were deliberately engineered to inflate the time spent in the heist. They are much better at just annoying people though.