Prove it .. beyond a reasonable doubt!!
I am in agreement with you that comp checks should not be done, but that is a personal business decision, its not against USPAP and its not against the law. Is there a question regarding the second assignment? You bet. Thats a main reason I dont do them (well one of the reasons anyway). As far as proving the second value was predicated upon the first, I personally think it would be very very difficult to prove, especially if the first report states that the value could change upon full and complete inspection of the property and preparation of a full report.
I dont disagree with your thoughts, but that doesnt mean they are correct in the "legal" sense, nor does it mean that a comp check and second report cant be done in compliance with USPAP. That is what I believe the ASB has stated.