Incorrect.
While the front line CBP Officer could not have revoked GE, a supervisor could approve a recommendation and that is close to a certainty of a revocation.
No, just because the Officer could have effectively revoked OP's GE does not mean that he would have. For the most part, CBP handles routine stuff just fine. An extra bottle of booze, a forgotten purchase. It happens. The key is to be honest about it and it's rare that it amounts to a hill of beans.