Did a bridge column make errors in discussing a hand?
No; swap the club 5 and 6 and South still makes the hand. Deal it out with a deck of cards and see. 

If West wins the second club and returns a diamond the diamond loser has been eliminated; if West returns a club the 4th club is now set up for the diamond pitch; if West returns a trump or heart Declarer wins and leads out the 3rd round of clubs, wins the diamond return by East and goes to board with 3rd round of trumps to pitch the losing diamond.