Its a typo, he meant the 190µ bag is a cleaning bag. Keeps crap out of the 160µ bag/hash.
Depending on the material, and the mixing time, the 160µ hash may or may not be pleasant to smoke. Sometimes my 120µ is like raw sugar crystals, but without the 160µ above it to catch the less desirable hash, it wouldn't be so nice. When I end up with the uber melty strains going thru the bags, its usually the 90µ that comes out fmcd, but without the bags above to seperate everything, it wouldn't be so. See the reccuring theme? More bags = better hash