Why is a special sand cloth used on hermetic compressor system?

My reasoning for the concerns are:

1. that something harder like garnet or ceramic can damage metal parts. Plumbers/HVAC sand cloth is made of Aluminum Oxide, therefore softer than metals used inside of the systems.

2. in the past there was some that used steel wool for prepping fittings and in these cases the metal particles would be attracted to the magnetic forces inside of a hermetic compressor or solenoid valves, etc. thereby causing problems.

Other than that I can think of no other reason. Some HVAC textbooks specify that a "special" sand cloth be used but I can find no other specific technical literature to support this statement. Bottom line, when you clean piping and fittings use regular aluminum oxide sand cloth/"plumbers cloth" or what is even better today is to use synthetic cleaning pads.

BUT MOST IMPORTANT IS TO CLEAN OUT ANY TYPE OF GRIT/WIRES FROM FITTING BRUSHES, ETC. - FROM INSIDE THE PIPING AND FITTINGS BEFORE JOINING. (Angle pipe/tubing down when cleaning, blow out fittings, etc.)