the script teleports xenon ships from their sector, does not create it from the air?

No, all active encounter ships are existing ships "teleported" as per the original encounter feature (but less often). This was to maintain the design Egosoft implemented and it helps regulate the numbers within the universe for performance, balance and economic reasons. The only ships which are generated from "thin air" are the ones which are salvageable by the player... but these tend to be relatively rare (and balanced using the player's fight+trade rank).