Yes, the statement is only true for the hypotetical case when no air is around the object (it could happen very high in the atmosphere, where air is very thin).
Thus, the friction forces are eliminated in order to measure the acceleration coming from gravity forces.

Read this link about free fall (includes video):

http://en.wikipedia.org/wiki/Free_fall

In real life close to Earth, as the falling speed increases, so does the drag force (at a square rate respect to the speed), reaching the object its terminal speed.

The point of the signature is to provide an idea of the dynamic of the forces that our planes challenge..........