I agree with admission, from what I know, and anyway admission knows more than me....
However an exra detail is that sometimes a local authority will create an extra reception class (a "bulge class") in a school to which allocations could be made.
Last year, in Islington, they created some bulge classes in schools which:-
1.Agreed to them
2.Were at least OfSted good.
- Near, or in, an area of high demand.
The practical effect of this, in many cases, was to "clear" the relevant waiting list, so that more parents got a place of a high preference, creating vacancies in other schools previously filled in the first round, and so on outwards in a ripple.
So that meant the level of "churn" after offer day was higher than usual, and by the sutumn the number of pupils "allocated" was trivial, and to a close school.
Mind you it would have saved some stress if they had created the bulge classes BEFORE offer day, but the authority are, understandably terrified of creating too many places due to the cost of having a surplus. So they hung back until they could see exactly what was happening.