If you agree that 3 makes for an easy roll, then it’s only an easy roll if you remember it and have thought it all through. If the player points it out when ask

If you agree that 3 makes for an easy roll, then it’s only an easy roll if you remember it and have thought it all through. If the player points it out when asking the guard, they have achieved the same outcome by making sure you and the guard you are role playing understand the situation via real world persuasion. You’ve just shifted the burden of persuading the guard via roleplay to persuading the dm via contextual reminders which is less cool.