he probably welded the front and 2 sides and didn't want to bother with the backside.......lazy , cheap , half-assed........
who cares about what "other" contractors do,,,,,tell him your not interested in whether or not its strong enough,,,,it probably is,,,,,its a workmanship issue,,,,,,,,,,,,,,,,you know , a monkey can tack coat hanger racks together for K mart,,,,,,tell him to do at least,,,,a little better than that.......