As a couple of us have pointed out before, rudder makes a plane bank because, when the rudder induces yaw, that yaw makes the plane bank because of the plane's dihedral. That's how three-channel planes turn. It doesn't look quite right, but it works, but that's because of the dihedral. Without dihedral, yawing won't create the bank and you'll get a skid. Whether a plane with ailerons needs rudder input to make a turn that looks good from the ground depends in large part on size (larger models tend to need rudder), on whether it has aileron differential, and on how much dihedral it has. My club has a plane which, before I built a new wing for it, had so much dihedral that giving it aileron input with no rudder would make it turn the wrong way (i.e. left aileron would make it turn right.) We call it the trainer from hell, and we use it only as a paintball target. As a rule, three-channel trainers have more dihedral than similar four channel trainers.

I don't think anybody in this thread is trying to discourage you from learning to use the rudder. We are trying to discourage you from getting into the habit of making ordinary turns unnaturally flat by using rudder and opposite aileron, because someday, if you routinely do that, it will cost you a plane. Once you've learned the right way to turn, you can play around with skidding turns, slips (useful at times) and lots of other things. But that video you watched is dead wrong.