Most crypto exchanges support both exchange account and margin accounts.
Exchange accounts allow you to exchange on crypto/fiat to another (e.g. USD to BTC). When trading exchange accounts. Exchange accounts do not allow short trades.
Margin accounts allow you to have long and short positions on any pair (e.g. long BTC/USD or short ETH/BTC).
SimpleOrder property exchangeOrder (which is false per default) drives which account you are trading against:
exchangeOrder = true means use the exchange account
exchangeOrder = false means use the margin account
Note that every exchange differs on how to submit exchange account vs. margin account orders.
Some require you to use different securities (e.g. Bitflyer), others different order types or price types.
Please refer to the various exchange documentation sections for details.