It was a small claims case, so there is likely no precedent. Your are right though, he should appeal. In my state, if a small claims case is appealed, it is always heard fresh ("de novo")
Revising contracts with binding arbitration clauses has some recent precedent in the Supreme Court of the United States. Epic Systems Corp. (not the game company) sent employees a memo which can be paraphrased as, “you can no longer class action us. If you keep coming to work, you show you agree to this change.”