What happens when your order is sent but the exchange never replies?
Most order-handling code is written as if there are two outcomes: the order worked, or it didn't.
There is a third, it is more common than people expect, and it is the one that actually costs money. You send an order. The connection stalls, or the venue returns a shape you don't recognise, or a gateway hands back a 502. You now do not know whether you have a position.