eBay Managed Payments One Time Payment For Balance Due
eBay has added additional options for sellers to pay when there is a balance due on your Managed Payments account.
In eBay Managed Payments, fees and refunds are deducted from the seller's available balance. If a refund caused that balance to become negative, previously eBay would simply deduct those funds automatically back out from the bank account on file.
Now it appears eBay has added an option to make a one time payment to cover the balance, with the seller being able to choose to make the payment from either the bank account on file or a credit card.



Some sellers prefer to use credit cards to pay for fees, shipping and even refunds for cancellations so they can receive reward points. Other sellers may prefer this method to avoid possible overdraft fees if they were not expecting eBay to hit their bank account for a balance due.
eBay also recently added additional options for sellers to fund refunds for returns via credit card rather than Managed Payments balance.

After this morning's payout, my available funds are in the negative because of ad fees from morning sales. The amount of my pending funds far exceeds those ad fees so I do not have the option to make a one time payment even though my available balance is in the negative.
The same thing applies to the article I wrote that you linked above. The option to pay for refunds with a credit card or bank is only put into action after your available/pending funds are too low to cover the amount. The difference in what's owed can be charged to one of those backup payment sources.