TIP: 99 Century (or others) windshield-wiper repair

While driving in a heavy rainstorm, a windshield wiper failed (apparently stripped at the hub). Fortunately, it was the passenger side or we would have been in serious trouble. Two GM dealers did not have one in stock, but one had started to remove it after removing the hex-nut, but it did not seem to come off easily so we left it on. (a replacement wiper-arm would cost about $33). I was prepared to purchase the first one available, as well as also replacing the driver side on the assumption that if one went bad, the other might not be far behind. Fortunately, I dropped by a small town repair garage to at least learn how to remove it. He SIMPLY put a socket wrench on the nut and tightened it down with a substantial amount of torque (even thought it was not loose before). He also torqued down the driver's side, which should prevent it failing in a similar fashion. He didn't explain any theory of what had happened but he approached it with a certainty that I believe he had experienced this before. His charge was so low that I felt obligated to give him a substantial tip. (Do any mechanics out there challenge this solution, or have an explanation of whether some irreversible damage has been done to the hub? It has continued to work fine during more rainy drives). If this is a satisfactory solution, it occurs to me that it would be an extra- ordinary opportunity to be dishonestly exploited in a rip-off.