Maybe they say they taking them as a polite way to say they are checking them befoe granting FLR etc.
That straight away surely puts up the costs and means it cant be all done by post?
Going by the pilot I think that's the idea - they check your identity again before they issue you with the visa/identity card. And yes even if you apply by post at some point you'll have to go in to have your biometrics captured again.