I think the rule is in place because there is a risk that transfers can go very wrong, and Disney can say "not my problem, it is against the rules". They are not going to step in and prevent it, but they are not going to get involved in the event of fraud.
To me it is analogous to an ACH transfer at your bank, versus a wire transfer. The ACH transfer is of a limited amount. It takes 2-3 days. If something goes wrong, there is time to reverse the transaction. A wire transfer, on the other hand, is instantaneous. It can be for very large amounts. There is no recourse if something goes wrong. You could send a wire of $1,000,000 and it could be further wired through 5 shell companies before you realized anything was amiss. Wire transfers are a great thing, and people use them all the time, but it is best to use them in a transaction where there is complete trust on both sides.