Aren't we all getting a bit wound up over this? Surely it's simple.... the instructor feeld safe and he signs you off. You make him nervous and he'll ask you to go up again and see if he feels safer that time.
Let's not underestimate the skills of our instructors, they may sometimes have less hours than a pilot they fly with but they've been trained to a far higher standard than the average PPL. (No I'm not an instructor either)
For what it's worth, I found talking through the way I pre-flight, communicate, rejoin etc with the instructor gives him the opportunity to suggest better/safer ways of doing things as you fly. Surely this is better than a silent hour when you really don't know what he's thinking and then being hit with bad news back at base.