It's only a 'free loan' if Tesla takes your money and doesn't ship the product.
From what people have posted above, the charger options are included on the order page for convenience but are actually treated as separate store purchases. If this is the case, I expect they would be treated like any other store purchase: the item is billed and shipped immediately if it is in stock. If it is not in stock then your information is held and it is billed and shipped once available. Either way, you are paying at the time of shipment for the product so it's not a free loan, it's no different than any other store purchase.
Getting the wall connector ahead of time makes sense since it can take time to arrange for installation. The mobile connector doesn't really matter, but since it's not in stock I would want to order it with my car to minimize the chances of not having a means of charging once my car arrives. This does raise another question - with the mobile connector on backorder, I wonder if Tesla will prioritize orders linked to car orders over general store orders, since they are more likely to be customers' primary or only means of charging?