I've done little work post 1861 census but universal compulsory education only came in in the 1870's - even today it is estimated that about 20% of population is functionally illiterate but at end of 19th century I suspect the enumerator had to fill in the form from whomever he could find on the Monday - in large cities with multioccupancy and somewhat untidy (as viewed from a middle class) family structure coupled with an attitude that the census would be of no benefit to them and might well be prejudicial there would be little real pressure to be truthful - I'm more surprised how accurate most Manx censuses actually are.
On the web page I gave a reference to a couple of papers from the Local Population Studies group - they have published much more and consisder some of these points