I would argue that both are bad game/story design. Unless the skill is a plot point, it should not change the chance encounters in the world your players are in. Both of these examples are meta-gaming. The NPCs of the world didn't know the player characters had that ability, and should not change their actions until it is known to them.
I had one DM who was huge on meta-gaming, and at first I thought it was just some peev of his, but honestly after a while and understanding it better- it made a better experience. It now makes me annoyed to see it used and I better understand his rants...