Normally if you refund and cancel a transaction, you won't be charged merchant fees.
If something goes out of stock unexpectedly, or supplies are slow, you'll just refund the customer, cancelling the contract of sale and any obligations.
But, under new March 2020 PayPal terms, vendors are charged FULL % transaction fee on refunds unless "voided".
Other merchants will likely follow.
The only way to avoid paying these fees is to "void" the transaction.
Currently vendors cannot pre-authorise Express Checkout, classic PayPal, nor other merchant transactions, which means they can't "void", and will always pay these fees
There are also implications if terms stipulate the "contract of sale" does not begin until payment is accepted. (Protects vendors)
This request is to add the standard Pre-Authorisation process for PayPal, and other card merchant configuration, so that if vendors are unable to ship an order they can "void" a transaction, and avoid any charges for refunding the customer