Answer: So if its regular, you would always tighten it. Here's the reasoning: "When you lower the pitch by releasing tension, there might be slack in the gears in the tuning machines, which might make the string go below the intended pitch.
Step-by-step explanation:
"When you lower the pitch by releasing tension, there might be slack in the gears in the tuning machines, which might make the string go below the intended pitch. By going further down and approaching the target note from below, there will be force applied to the gears and when you've reached the correct pitch the gears have less potential to move. So your teacher is correct."