It is not a return: there is no parcel coming back, so there is no return processing cost and no restocking. Treating the two the same overstates your logistics costs and understates your fees, which is why a chargeback and a return are not the same cost.
In a P&L the disputed amount belongs with returns and the fee belongs with transaction costs, attributed to the gateway that charged it, and that is how the nouz statement is built to book the two halves. It does not read Shopify's disputes, though, so today a lost chargeback and its fee are missing from the statement. Shopify lists them on its Orders page under the chargeback status filter, and they belong on the month-end checklist.
A handful of chargebacks is a cost of taking cards; a rising rate is a signal about fraud, product claims or delivery times, and it deserves attention long before the fees hurt, because providers price and even terminate accounts on it. The payment fee calculator carries a chargeback line for exactly this reason.