Actually no it’s not and it does not guarantee anything at all, one of the person can send an empty box if their intent is to scam someone they will.From what I have read of Trades, it is typical for both parties to send their animals out at similar times, so that each party has a tracking number and it limits the problems for scamming (not by much, but it's a quicker reassurance).
I generally do not do trade however trade come down to the person’s references and or reputation.
If someone wants to trade their animal with me THEY will have to ship first, upon receiving and inspecting the animal I would then ship the animal that was agreed upon, works the same as receiving payment, you pay first get the animal once paid, here is you send your animal you get yours once received.
If I was contacting someone to trade my animal, I would expect to ship first.