I can tell you the assignors do take more care in picking who the center referee is during playoffs. In the first round, it may be that the less skilled but qualified referees get their "reward" (because they work hard also)game early in the playoffs vs. later in the playoff rounds.
That being said, highschool referees do not have to go through the amount of training the club referees do, and there are several HS referees who are NOT club referees. This is really where you see the differences in my opinion. Talking more to the players or "warning" them as you stated is more of a US Soccer (club) directive and is not really talked about much in highschool soccer. That is not to say that referees should not be doing it but if you are only a HS referee, you (the referee) may not have been taught how to talk to a player effectively.
