The School's Adjudicator already agrees with you on the timing aspect, mystery. This extract is one of 11 recommendations made in the S.A. report covering the period September 2008 - August 2009:
A major cause for concern is the date up to which objections can be made to admission arrangements. Specifying a date by which objections must be made is a definite improvement on the previous requirement to lodge an objection within six weeks of the arrangements being determined by the LA or the school. However, the deadline of 31 July is problematic. Most objections that arrive in July cannot be investigated properly as schools approach the end of the school year, and then close for the summer holiday. This leads to considerable uncertainty for all concerned. Although it is understood why this deadline was set, to allow parents as much time as possible to object, an earlier date of would at least allow investigations to begin, and hopefully in many cases be concluded, before August when many schools are closed.
Presumably a new report should be published shortly and that will show whether there has been any progress.