The short answer is yes. Phones want to maintain their high quality accessories and reputation, and they will no doubt create a process for their USB-C cables that requires MFI certification. While this doesn't make the USB-C cable different from any other cable you'll find at an online retailer, it reassures customers of the phone that their USB-C cable has passed the rigorous testing and manufacturing that consumers already know and associate with the phone product.
The short answer is yes. Phones want to maintain their high quality accessories and reputation, and they will no doubt create a process for their USB-C cables that requires MFI certification. While this doesn't make the USB-C cable different from any other cable you'll find at an online retailer, it reassures customers of the phone that their USB-C cable has passed the rigorous testing and manufacturing that consumers already know and associate with the phone product.