A player fails a medical or doesn't agree terms, for example.
Then the money is refunded surely - yes the board have made mistakes, but they're not THAT stupid.
Think it as a guarantee of exclusivity - we credit the money to your account. You bank the interest now. Only we get the right to talk to the player whilst you have our money. Deal goes belly up, we get the cash sum back, you keep the interest, deal goes through, consider yourselves already paid.
Very clever - stops other clubs jumping in with more cash at the last minute.
If Julie is correct....then it wouldn't be surely.
I think this may be the exception rather than the rule.