The tendency for project promoters to overstate demand is common and certainly not restricted to MAN's R2, or to the UK or even to airports. Worldwide this goes on when project promoters - roads, runways, railways, bridges etc want to persuade governments or private investors or banks to part with their cash to build their pet project.
I remember blanching with disbelief at the traffic projections even way back then and also the long forgotten mantra 'airlines are queuing up to get into Manchester'. From a very quick glance at some of these projections at the time, I seem to recall that direct services to Indonesia with Garuda were seriously expected to be in place by 2010. Made me laugh even then.
BHX overstated the need for very long haul services to justify their runway extension too.
Enjoy watching the hyperbole over the 'new runway in the SE'..........in fact there should be a prize for the most ridiculous over the top claim about what might happen in the event of there being no runway.
This happens. It's a game - albeit a very expensive one.