Lot of people don't know what Jams is
JAMS is the arbitration service. His counsel didn't join the opposing counsel, she joined JAMS, in the office of the arbitrator. It's not clear why your lawyer joining the arbitrating judge's office would make them biased against you, but that's what he was claiming. The real judge threw that out saying if he wanted to make that claim he would have had to object at the time rather than waiting to see the award and then making the objection.