As I'm sure you know, that issue was investigated in quite a bit of detail on another forum, and the conclusion was that any 'fudging' only made a difference of a few percent to the reported clearance rate, and would be reasonably consistent with 'fudging' levels that have existed for the past couple of decades anyway. So clearance rates are no more or less reliable now than they have always been.
To summarise that discussion, what you call 'fudging' is just basic human nature. Some agents don't report their results on Saturday in time for the initial clearance rates to be released on Saturday evening. Those results then trickle in during the following week, and the initial clearance rates are then revised and re-released the following weekend. On 25% of occasions, the clearance rate is actually revised up rather than down. Overall, the average revision during 2010 was -2.5%.
I have read on those forums and particularly that post. I think you should re-write it "the conclusion" to "my(shadow's) conclusion" as your research was not anywhere near definitive and was actually shown not to be correct. We have also seen via apf.com rpdata that recent clearance rates for Melbourne for the single weekend went from 68% to low 50% range after some unreported auctions were reported. There is still a huge amount unreported though which may bring it down even further.. I will try and dig up the link.