Both credit cards and BNPL allow you to purchase items and make incremental payments. Credit cards don't enforce a specific due date for each purchase made. Instead, there is a due date for your statement balance or at least the minimum each month.
BNPLs are like short-term loans. You'll have a predetermined number of payments to pay for your purchase. Those are all scheduled, so you must meet them to ensure you don't incur late fees.