I don't mind trying aural tests, even singing (tough luck to the poor examiner who has to listen to me, that's my philosophy!) but I don't see how sight singing has anything to do with "aural". Aural is about the ability to listen, I believe. So other than listening to yourself make a noise on an instrument that probably isn't your choice, I don't see how sight singing falls under that description.
Of course if I do do ABRSM exams in the future, I will fully embrace that, and get myself to the standard required, and anyway, it would be a nice thing to be able to do. I just don't see it as part of an aural test, and I can really understand those who feel embarrassed or particularly worried about it. I think ABRSM should find different tests to measure the skills they're looking for.