A player working in programming speculates that the design in GTA VI where pedestrians notice and react to being followed might also serve to obscure the boundaries of NPC schedule simulation. A previous IGN interview mentioned that pedestrians might react to stalking, but this technical application has not yet been confirmed by Rockstar Games.
According to this player's hypothesis, if a player follows a random NPC for an extended period, the NPC might turn around and demand that the tailing stop, or display hostility. This would allow pedestrians to respond to the player's actions and could also prevent the player from continuing to observe their destination. The latter use case is the player's speculation about the design intent.
The discussion uses the daily activities of residents in Red Dead Redemption 2 as a point of reference. Based on players' estimates of the map scale in Leonida, creating complete daily routines for every passerby in GTA VI individually would be an extremely complex task.
The article also imagines a rooftop bar scenario: NPCs could combine behaviors such as posing for photos, drinking, waitstaff checking tables, and leaving seats, making close-up observation feel natural; if a player continues to track someone all the way to their residence, the system would need to handle the endpoint of their movement. This is merely an analytical example and not a confirmed implementation in the game.
For comparison, the article also mentions the townspeople in Kingdom Come: Deliverance 2, as well as NPCs with homes and jobs in Watch Dogs: Legion. Different games can implement pedestrian simulation to varying degrees; the specific approach taken by GTA VI remains subject to official confirmation.