According to the Tire Rack website, http://www.tirerack.com/tires/tirete....jsp?techid=77
, the puncture must be repaired "inside" and "through the tread" to properly seal both "air leakage" and "water intrusion". From my experience with flats, the "inside patch only" repairs seem to be the most common and the "plug from the outside" seems to be the quickest, but not usually done these days. I don't remember anyone "plugging and patching" one of my tires, although it could have happened.
Here's a picture from the Tire Rack website explaining that "inside patches" as well as "through the puncture plugs" are incorrect. They suggest that an "inner patch and puncture plug" are the best approach. Rationale is to seal the tire against water getting into the tire through the puncture, possibly damaging/rotting the cord as well as the steel belts.
With the "known stress" we place on ST tires, I think I'd relegate any "repaired tire" to spare duty only. I wouldn't put it on the ground as a "trusted tire"......