They don't like the idea that we don't try and say we have the exact numbers. We come out and give estimates, preliminaries, etc and always adjust when new data comes in.
VGC is simply trying to have the most accurate data possible and the quickest way possible. Some see that as bad because we use other numbers to improve our accuracy and thus assume that we have no idea what we are talking about. However if they would actually consistenly look at our numbers are right or close to what is perceived to be right the majority of the time and use outside numbers to only maintain that accuracy.
I think it's great that we do that while others use it as a complaint against us. But ignorance doesn't get them very far.