Up until a week ago, special meal requests were coming back in the GDS as UN - Unable to Confirm - Not offered on this route.
So either a deliberate decision not to offer special meals on this route (perhaps due to the short flying times and single crew member) or an oversight when they introduced Club on Domestics.
It does appear to work now though (with 24 hours notice).
Given that the system was responding with a 'no' at the time the requests were being made, and BA were therefore stating the meals would not be loaded, I can understand the reluctance to compensate.