The coking problem is genuine, and may be influenced by operational techniques.
Tactical aircraft oft perform rapid turnarounds, reloading/refueling as fast as possible. If the engine is shut down soon after high-power ops, and if the engine has an oil-fuel heat exchanger in the high-pressure fuel manifold, the hot oil works on the static fuel mass and may boil the fuel, inducing fuel vapor into the hot combustor, and causing a brief post-shutdown fire. Probably not harmful, because of brief duration, but likely exciting.
In the commercial world, a proper cooldown period is important to prevent coking, especially when T900 "normal" oil temps are as high as 180C. In thinking about A380 ops, since only inboards are equipped with reversers, they are likely to see hotter oil at shutdown than the outboards.
And so it is
possible that something in QF shutdown timing technique is aggravating the coking problem. I suspect QF and R-R are already examining this issue.
