There is a point though - Mastercard and Visa treats them as "prepaid" credit cards, which are different from both true prepaid cards (as issued in the US), charge cards, and true debit cards (former Maestro and Visa Electron). Again, different regions have different lines for this, especially in Europe.

IIRC, bunq in the Netherlands issues Mastercard "credit cards" (with no "debit" annotation as on true Mastercard debit cards). They're treated as credit cards for Mastercard purposes but are backed by deposits.