There is an inherent "delay" in power response for a jet engine. There are a lot of variables: engine design, altitude, current power setting, and many others. At low altitude, where the air is thicker, power response is better. At higher power settings, engine response is also better. For example, if you're up at 90% thrust, your engine will response faster with power corrections, as opposed to being back on the throttle, say 75%. As for what you're hearing on landings, the pilot is trying to maintain a specific glideslope, which requires multiple power corrections, as well as slight attitude corrections, in order to maintain that. You just can't select the perfect power setting, as everything is changing all the time: weight (fuel state), winds, for carriers the ship is moving, etc.
Does that help?
Yes, that is exactly what I was looking for. thanks!