That is because only one wheel is bring turned, the abs module is trying to stop the wheel as its assuming the car is spinning on ice road.
Please dont let idiots work on your car, they will cause you massive monetary loss.
To test the abs speed sensors, pull up the individual wheel speed sensors PiD on the scan tool and see what is happening as the car goes on road, all wheel speeds should be equal when going straight.
If your tool is not capable then test each sensor with an oscilloscope. But you will eventually need a deep level scan tool for diagnosing and resetting abs unit
Also check what exact fault codes are being recorded for abs unit, it maybe something else entirely like a failed pump due to wrong technique of repair when changing brake pads or simply rusty brake fluid jamming the pump.
Once again, if you own a car with abs, esp etc etc dont visit small time shops that do not own advance level scanners.