Is 4WD real 4WD?

What is your question?

I have a 2005 hyundai tucson v6 4WD and have the 4WD lock button. I was reading the manual that says "This setup begins to get cancelled when the vehicle speed exceeds 30 km/h and the function is completely released at a speed of 40 km/h or higher. So if I'm driving at higher speeds with the 4WD lock button on...am I still in 4WD? Can you really call it 4WD if it turns off and on like that? Never had a car with 4WD so I'm not sure...any help is appreciated.