Huh? It has nothing to do with a training plan. But since you brought it up, doing intervals will usually result in higher normalized power vs average power. So will riding up and down hills where you put out more power going up, and less power going down. If you ride at exactly 200W, then normalized and average power will be identical.
Like stevemz said above, normalized power was created to equate training stress to rides with different power variation.
The normalized power model is based on how much blood lactate accumulates in your blood based on power output relative to threshold/FTP power. Higher power = more lactate = more strain / training stress. Lower power = less lactate = less strain / training stress.