It will stop SOME of the oil. Otherwise it wouldn't get soaked with oil.
On my system down here, my old sole LPG bus and one ton Chevrolet, I had reservoirs for oil to drop out of the gas followed by filtration. Over a period of say a month or two it was not unusual to drain in excess of a pint of oil. It is a matter of where their system picks up suction for pumping and how faithfully they check for contamination and blow down for flushing.
A lot of what mechanics see with contamination can be compared to operating an engine oil filter for two hundred thousand miles without servicing. They see sludge and dirt. It should not be claimed the filter is not doing it's job. The problem is the filter is ignored for years.
In a refinery, LPG cannot be processed devoid of lubricant. Secondly, odorant is a liquid injected into the process stream it is not a gas.
I accumulated over 200,000 miles in the seventies and eighties running LPG exclusively. I always had at least fifteen filters on hand. Dirty filters passed contamination and clogged a vaporizer or Imco 425 carburetor. And that is something a person does not want to deal with on the side of the road.
The filters are utterly unsophisticated.