I'm sure the 777 boys will be along shortly to add their comments but as a jumbo driver I can tell you I've never seen it. It's too transparent and I'm quite sure any decent CSD would raise the question of why there were invol downgrades from First with a flight crew rest seat there. If the case was settle without contacting the operating crew then it's plausible someone at the outstation has found a watertight means of covering their tracks. Having racked my brains the only situation in the last 10 years I can think of where flight crew were entitled to a First seat was one season on the IAH route when BA wanted to use a non-bunked aircraft when the route required bunks. The First seat was blocked out as a compromise deal as Club wasn't suitable for proper horizontal rest, and again, the seat was blocked out in the commercial booking engines. Apart from that if there are invol downgrades going on then somebody is on the fiddle!