I think the only “error” Horowitz made was saying there was no proof of bias. He didn’t need to put that in if he is looking at the facts. For instance, “Oh by the way, there was also no proof that the coke machine had run out of cokes.” Like this example, the “lack of bias” statement is an unconnected thought to the process which was to discover the FACTS (not opinions, motivations or misc “weather reports”). The report did this, it found the errors and the facts. Had he left out the “opinion” of no bias found ... it would have been a perfect report.
Horowitz also said that the people claiming to be exonerated, should be celebrating because he has forwarded this information to the Justice Department.