When you match speed the engine is spinning to the speed that the wheels are spinning at, depressing the clutch is not necessary. At a certain RPM, depending on the gearing of the car, you will be able to do this.

Just try upshifting one day without using the clutch and allow the revs to drop while pushing lightly into the next gear. At a certain RPM, it will go into gear very easily.

 

my dad could do this in his POS (i mean POS) 85' mustang GT, it was only firing on like 3 out of the 8 cylinders, and had about 40 hp/torque, he would shift from 1st to 2nd to 3rd, with no problems at all, but from third to 4th, he had to clutch, i tohught it was pretty cool, considering it was aPOS Ford