Why is it when you are at a plate conference the umpire tells you he has a small strike zone and tells you to tell your players to swing...
Because the umpire is obviously either: Untrained, or; Trained, but thinks he knows better than his trainers. Neither is a good thing, but the latter is probably the worst. If someone is willing to listen and learn, they will. If not, well, you can't really change a person's personality.
As a matter of good game management, an umpire should NEVER go into any detailed descriptions about how he's going to call the strike zone, or lay out instructions about "his" strike zone. It can only lead to confusion, complaints or confrontation for the coaches and players.
The pre-game plate conference with coaches should consist of:
1) Brief introductions.
2) Taking the lineups from the coaches.
3) Going over the ground rules.
4) (Optional, depending on league or association). Have coaches confirm if teams are properly equipped (Mandatory for high school ball).
And that is it. Circumstances might dictate a coin flip to determine home team, or confirming any time limits or special rules for a league or tournament. This entire meeting should take about two minutes, tops.
The pre-game conference is not a rules clinic and time should not be spent with unecessary explanations of standard playing rules (unless a coach asks a quick question about a specific rule) or having an umpire go into detailed explanations about "his" strike zone or "his" particular philosophy about how he's going to call the game or interpret any standard playing rules.
Now, the umpire who told you this was not only doing the wrong thing, but he was doing it the wrong way. "I have a
small strike, so tell your player's to swing", doesn't even make any sense. A small strike zone would encourage batter's to
not swing. If you want to get the bats swinging, you would need to call a
bigger strike zone!
The essence of good game mangement is for the umpires to keep control of the game. Going off on goofy tangents at the pre-game conference can start the umpires down the slippery slope of losing control of the game- before the game even starts!