I don't want to speak for ZekeKelso, but here, IMO, is how it is more complicated. For a cash rental, the owner call, makes your ressie, you send cash. A pretty simple transaction, though there are risks.
Now, for a trade/swap you advertise, for example, that you own BCV and want to trade to BWV. A BWV owner reponds and makes your reservation (yay!) and you call, only to find there is no availability at BCV for the owners date.
Do you then pay for the points, and make it a cash rental. Do you cancel the reservation? Do you allow the reservation to stand, while going on a waitlist? To many "what ifs" over a standard cash rental.
What if they want their vacation before you want yours, and they take the vacation, then cancel your reservation? They are still strangers, after all.
Do you require a cash deposit, sort of an escrow or performance bond, on both sides of the transaction?