So the implementation can be such that it can depend on the merchant whether or not they want to bear the MDR, big brand outlets like Pantaloons, lifestyle, etc who have big profit margins won't mind bearing the MDR like they do for CC and the small local stores won't agree to bear it.
So if you have used PayTm for business, you would have seen that option, only if you agree to accept CC payment, the customer will see that option when they scan your merchant QR code, if you have not agreed to it, they will only see the option to pay through bank account.
The same can be done for merchant UPI QR codes, if the merchant doesn't agree to bear the MDR, the user will see the credit card option greyed out when he/she scans the QR and only see the option to pay through bank account.