I have a feeling that the "Comey broke from procedure, but did not display overt bias" refers to one specific act of Comey's.
That act refers to his taking the decision about prosecuting Clinton from the DOJ, and making it himself. His reasoning was that it would have looked even worse if the decision was made by Loretta Lynch following the publicity about her meeting with rapist Clinton on the tarmac.
Regarding Comey, the I.G. has a huge number of other actions and decisions to consider.
One tiny aspect of the report has been leaked and spun.