Maxperson
Morkus from Orkus
The narration isn't a part of determining what the PC knows. The narration is the culmination of the PCs actions and the monster's actions.In the example provided, the DM can choose from one of many options when narrating the result of the adventurer's actions. They chose an option that leads to uncertainty when the player has knowledge that the roll is low which puts the player in the position of having to decide whether or not to act on that knowledge. That is the DM creating the opportunity for it to occur. They could have chosen otherwise as I have shown.