Shimy, interviewers want the best they can get. So it makes sense to make the candidate comfortable and more able to give a full and fair account of themselves. It is part of the selection, and in the recruiter's interest to avoid bias and ensure relevant scope.
Sometimes this can get a little lost in translation, and it is true that jobsworth-types can be found in unlikely places. It can help to tell candidates that it is more important for them to 'test' the recruiter than the other way around. It is a chunk of your once-and-only life, while you are only one of the next batch of livestock, so to speak, to them. Obviously both parties should be respectful, but it is a two-way street.
MrKlaw, I think that Maths has been seen as a soft option for A* GCSE students in the past, especially STEM students that needed a 3rd subject, and syllabi that could be taught to the test. That applies not just for Maths. In my day for example Maths was at least as challenging as Physics, but for over at least a decade that has not been so. Having A level grade boundaries that are more spread and less high are seen as more fair by teenagers, even the ones who cry during the papers. How badly you feel during a test is not a reliable indicator of your relative success. Science candidates from the last two years have already been through what Maths has this year.