I think you have to consider the differing and somewhat divergent points coming up here. I agree its unfortunate that they seem to be taking this approach to this (and one presumes other things of similar ilk) although its also worth accepting I feel that it *is* a somewhat small percentage of the whole UK population. Sadly, I can easily believe that a greater percentage of people make mistakes on the census than are in poly relationships. Given how many misunderstand “10 items or less” or “Diesel”…..
Anyway – that aside, I don’t think the ONS will have a massive anti-poly or indeed anti-anything axe. Likely as not they are simply civil servants trying to get the most useable data they can. Assuming all inputs you receive are perfect strikes me as a very silly idea, even if, unfortunately, that does sometimes means actually blurring your picture slightly.