The map modes that show the player icons making circuits around the screen relative to their positions seem to work fine; however, the maze is so complicated that determining the racers' current positions is impossible, so the players' mugshots will just be replaced with question marks.
Were question marks used instead because of a hardware limitation on the N64 itself? Meaning the N64 couldn't keep track of all the racer's positions in real time? I don't think impossible is the right wording, because the first place kart is flashing rainbow on the minimap during the race, so the game tracks the kart in first position.
Or were question marks simply used to add some more fun to the multi route track, and never knowing where you're at exactly when playing?