That information is absolutely false.
You want to make sure you fully disengage your clutch when you shift, everytime. If you don't, you risk clipping the teeth on a gear, and a slipping clutch can glaze and/or wear faster.
The other thing is sitting with the pedal fully depressed will wear the throw out bearing faster. So if you're sitting at a red light, put the car in nuetral and let the clutch pedal out.
The amount of excess disengagement will have zero effect on clutch wear.
Also, never rest your foot on the clutch pedal. You shouldn't touch it unless your going to use it.