I'm just guessing, but in my business as a sales rep, I've seen similar results when plastic media is used in place of traditional abrasive tumbling media. And where do they get the plastic media, you might ask? What do think happens to all of the holes that are made in plastic buttons?
Dunkin Donuts made a fortune selling donut holes and years ago a button manufacturer found a a use for his scrap products.
This process is very compatible in the medical device industry as no toxic chemicals are used to polish the metals that may enter the body in a surgical device. Done correctly, it will pull even baked on powder coat right off of stainless steel parts and leave the metal looking beautiful, without scratching or etch marks.