It's not a Creditable Refund; it's a deferral for something not yet paid, so it isn't also considered past due.

It's part of parity for the Self-employed to be treated as employers are treated for the Form 7200 provision.

"Employers that have already deposited all or any portion of the employer's share of Social Security tax during the payroll tax deferral period may not subsequently defer payment of the tax already deposited and generate an overpayment of tax"

"Employers that have already paid the employer's share of Social Security tax on wages during the payroll tax deferral period may not subsequently defer the payment of the tax"

Remember that SE = both an employer and an employee for purposes of the Social Security tax.