Well to be honest the new F seat isn't a dramatic improvement over the older one in terms of comfort...
From a marketing perspective however is LX steps up the C seat on the A340 and does not change the F seat, the difference between the two may get too thin to justify the large difference in fare (for instance, discounted C currently sells roughly at 1/3 the cost of F). Also it may not be good a marketing strategy to offer the latest product on medium haul such as DXB and in the future India and Africa, whilst offering the older version on ultra-longhauls to HKG, GRU, LAX etc..