Enjoy your free lunch. You are right. The FAA guy needs to get his basic flying manual out again. Any time the ball is not in the center you are in a slip. It is usually caused by rudder but also is caused by differential thrust. Not using enough rudder with an engine failure on a twin puts you in a slip. All slips are the same, just called side if you are using it to drift sideways usually into a crosswind and forward if you are trying to increase your descent angle on landing without increasing your speed because of the fuselage drag.