I haven't actually had it happen to me, but in some ways I can see their point. A lot of people DO say they're sending the money, but it never comes. I've had that happen to me. They're sending it every day, or else every day it's "I'm sending it tomorrow" and it just never comes. If I tell you tonight that I'm sending you a deposit on your horse, you can bet the money will be sent tomorrow, via the fastest method. I'm at the point where if I'm selling something & someone tells me they will buy it & are going to send the money, I outright tell them I must have payment within 14 days or else the deal is off. That way if I have another person interested, I can give them a definite date when I'll know if the horse is/isn't available to them.
If there isn't another buyer waiting & the money arrives 5 days late, then I can still complete the sale; of course if the payment does arrive late and the horse is gone, I would automatically return the check or money order. Anything else would be fraud.