USSSA Softball Dropped 3rd

[ekd4176]

Had a call made today that only the only plate ump thought was correct.

Scenario: USSSA 14u Open tournament. First base is open with 1 out. Batter swings at 3rd strike in the dirt. Batter runs to first, catcher makes bad throw to one and runner advances to 2nd. Home plate ump calls batter out because "the 3rd strike was caught cleanly off the dirt". I then heard him say that is was a USSSA specific rule. I have never heard of this. I asked the field ump during the next inning and he was at a loss as to what catching it "cleanly off the dirt" meant and thought it was a drop 3rd scenario. I cant find anything on it. Thanks