The enumerator will have left the return at the address a few days before, as they did for us in 2001, on their return, the enumarator would usually fill in the return in many many cases, as even in 1901, there was alot of illiteracy, expecially in the large cities where church and sunday school attendence was falling and children were ducking school to go to earn a wage. This is why there are often discrepencies between returns on place of birth and also why some relationships are muddled, the use of the term Brother-in-law was consistently confused with step brother and this was a common thing to happen.
Lodgers and boarders are often ignored when we do research, but infact there is a distinct difference, a lodger was usually someone apart fromt he family and would not be a relative, whereas a boarder was usually a relative that shared the family meal table, hence boarder, and so these are always worth looking closely at.