It's hard to imagine this being done for any reason other than disappointment with the number of applications, isn't it?
I recall that last year they received more than 7,000 and had made statements about hoping for 9,000 this year? Doesn't the BA FPP average more like 4-5,000? Last year Virgin got a lot of publicity via TV and national newspapers which probably caused a spike. It's hard to do that a second time around because news outlets are interested in, well, news.
By their own admission, a good portion of the applications last year were incomplete. The fact of the matter is that for a programme like this you are probably going to get about 4,000 serious applicants. I would also venture to say that any serious applicants who are going to successfully prove an established interest and commitment to aviation (i.e. pass the selection) will have already applied.
Perhaps they have set themselves an unreasonable goal and are now fixated on achieving it, even though the benefit of all those additional applications is arguably marginal.