Why is that odd? Surely if you want to make a case for a very expensive investment in a very congested location, as HAL does, you have to argue that the investment will improve connectivity between regions and the world and between the UK and the rest of the world in what is fundamentally a growth environment and thereby improve UK competitiveness. That is not odd. How else would you begin to assemble a convincing case?
The issue is whether those parts of the case are credible -- for example, will the market for domestic be fundamentally weak ;will HS2 trains be branded as BAxxxx with through ticketing ; will the northern economy improve or worsen relative to London? And so on.