Classifying method of control of 3D printers?
The question is if robots classification terminology the textbook sketches applies to 3D printing?

Servos (closed loop) are used in robots to guarantee position (you don't want to accumulate an error after repetitive movement), most 3D printers use open loop steppers that are instructed on a point to point basis through G-code instructions, implying that the use of servos is not a "requirement" for point to point control.

It is a requirement if you want to be absolutely sure that the position is reached. In 3D printing where the loads are generally low, this requirement is frequently dropped. But, there are printers that use servo control. 

Note that many CNC machines (operating at much higher loads than a 3D printer) even don't use servo's but (open loop) steppers, these are generally larger and more powerful (more torque).