Back directly on topic, for the first time yesterday I noticed that LHR immigration officers were asking all non-UK citizens using the EEA line where they were coming from. Though they could have used the e-gate if they had a biometric passport and not get asked. The information was not recorded, obviously, but I do not see how it is relevant.
Over the past year or so, I have not infrequently been asked on arrival at Heathrow where I have travelled from. (I am a British citizen and enter the UK on a British citizen passport.) I always simply answer the question, since I've got nothing to hide and I don't want to delay myself or the people beind me, but it has always struck me as odd.