It needs to be remembered that the purpose of ICC-ES is to make money. Their clients are the manufacturers who pay for the reports not the users of the product nor the building officials.
The whole process is biased in favor of the manufacturers who decide what information to share with ICC-ES and who often write the first draft of the evaluation reports.
If you look at the number of staff at ICC-ES and their qualifications and then compare that with the number and variety of the reports it is hard to believe that they have time to perform extensive technical reviews. It is also hard to believe that the ICC-ES staff has the expertise to review all products that ICC-ES issues evaluation reports for.
Yes ICC-ES has a history of not admitting mistakes and when they have no option but to modify a report, because it was flawed they try to sneak in the revised report without admitting that there was a problem with the previous report.