These are FACTS
Hong Kong Based Line Capts flying at least one freighter pattern in September is just shy of 50%, this could not be described as a small pocket of crew. This does not include reserve callouts or C & T. Very few Europe and NAM pax crew are rostered freighter flights.
These are assumptions
The vast majority have not voluntered to fly the freighter. This is vastly different from one year ago, and is going to get worse as more B744F arrive and crew resign from CX Freighters. The reason based crew do not fly freighters is they are flat out covering the Hong Kong crew unavailable to fly pax aircraft because they fly a significant amount of freighters. It could be the other 50% that fly freighters in October.
Funny old thing we told them this would happen the day they announced the ASL debacle.