But that is assuming (read somewhere - the mother of all stuff ups) the buyer is a serial non payer.

In this case the buyer offered to pay on a certain date so wanted to complete the sale.

To offer to the ability to cancel & the buyer takes up the offer this negates any repercussions on the seller  - the buyer cannot leave feedback at all.

Not sure the 4 day unpaid item thingo goes down well - buyers who end up paying  get 'huffy' - then leave the 'huffy' feedback.

Of course it is necessary for those that don't intend to pay.