This LEGO Mindstorms robot base is small, compact and packed in a very small volume. The goal of this constructions is to be used as a base and to show yet another way to experiment with adding motors to the brick.
90 degrees turn for the robot is different from 90 degrees turn for a motor!
90 degrees for the motor
Ninety degrees is a quarter of rotation of the tire. During a pivot turn, only that motor is turning. A quarter of rotation is very short distance and the result is that the robot moves only a little.
90 degrees for the robot
The expected result of a 90 degrees turn for a robot is that the robot is turned in the space 90 degrees to the side. That turn is very different from 90 degrees for a motor.