There is no evidence that WP status has anything to do with making D inventory available. All of the Oneworld airlines release additional D inventory upon request. There are some routes, days of week and time of day that has D0 and can only be released on an individual request basis. While FF status has nothing to do with it, fare basis does (there are many different D fares, and some pay the airline twice as much for the sector). Of course D is made available only if the airline yield management decides that is a "high enough" fare (i.e. no chance of selling it for higher), so you won't get D released for high-demand flights.